DEPT OF PHYSICS
| Researcher : Bai Y |
| List of Research Outputs |
| Bai Y., Ye M. and Wang Z.D., Entanglement monogamy and entanglement evolution in multipartite systems, Physical Review A (Brief Reports). New York, The American Physical Society, 2009, 80: 044301: 1-4. |
| Researcher : Beling CD |
| Project Title: | ICPA-12, 12th International Conference on Positron Annuhilation Defect Identification with Positrons |
| Investigator(s): | Beling CD |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 08/2000 |
| Abstract: |
| N/A |
| Project Title: | Porosity characterization of porous materials and polymers using positron annihilation techniques |
| Investigator(s): | Beling CD |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2007 |
| Completion Date: | 06/2010 |
| Abstract: |
| To enhance the functionality of the HKU positron beam by developing porosimetry characterization through the 3gamma - 2gamma ratio technique. This capability would yield industrially relevant information such as pore size, pore interconnectivity and porosity. To study the effects of in-situ electrical stressing and annealing of dielectric films. To test the capabilities of the CDBS (Coincidence Doppler Broadening Spectroscopy) technique as a tool for characterizing the chemical environment of pores. |
| Project Title: | International Workshop on Advanced Positron Beam Technology for Material Science (APOSB2010) F-Plasma Injection Studies on GaN Studied by Positron Beam Depth Profiling |
| Investigator(s): | Beling CD |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 03/2010 |
| Completion Date: | 03/2010 |
| Abstract: |
| N/A |
| List of Research Outputs |
| Fan J., Zhu C., Fung S.H.Y., Zhong Y.C., Wong K.S., Xie Z., Brauer G., Anwand W., Skorupa W., To C.K., Yang B., Beling C.D. and Ling F.C.C., Arsenic doped p-type zinc oxide films grown by radio frequency magnetron sputtering, Journal of Applied Physics. New York, American Institute of Physics, 2009, 106: 073709: 1-6. |
| Researcher : Chan HY |
| List of Research Outputs |
| Chan H.Y., Semi-analytical and numerical studies on the dynamics of scale-free complex network. Hong Kong, The University of Hong Kong, 2010, 1-55. |
| Chau H.F., Chan H.Y. and Chow F.K., On the critical packet injection rate of a preferential next-nearest neighbor routing traffic model on Barabasi-Albert networks, European Physical Journal B. EDP Sciences, 2009, 72: 641-655. |
| Researcher : Chau HF |
| Project Title: | Properties And Applications Of Quantum Low Density Parity Check And Related Codes |
| Investigator(s): | Chau HF |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2007 |
| Abstract: |
| To find new ways of constructing quantum version of low density parity check and related codes. To study the advantages and disadvantages of using quantum low density parity check and related codes in quantum computation, quantum cryptography and quantum information processing. |
| Project Title: | Quantifying Quantumness By Quantum Information Theoretic Means |
| Investigator(s): | Chau HF |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 10/2009 |
| Abstract: |
| 1) To quantify the quantum nature of quantum operations from the quantum information theoretic viewpoint. 2) To quantify the nature of multipartite quantum states from the quantum information theoretic viewpoint. |
| List of Research Outputs |
| Chau H.F., Chan H.Y. and Chow F.K., On the critical packet injection rate of a preferential next-nearest neighbor routing traffic model on Barabasi-Albert networks, European Physical Journal B. EDP Sciences, 2009, 72: 641-655. |
| Chau H.F., Tight upper bound of the maximum speed of evolution of a quantum state, Physical Review A. New York, The American Physical Society, 2010, 81: 062133: 1-4. |
| Fung F.C.H., Ma X.F. and Chau H.F., Practical issues in quantum-key-distribution postprocessing, Physical Review A. New York, The American Physical Society, 2010, 81: 012318: 1-15. |
| Researcher : Chen W |
| Project Title: | Theory of the ultracold Fermi gas in the optical lattice |
| Investigator(s): | Chen W, Zhang FC |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2009 |
| Abstract: |
| 1) To generalize the renormalized mean field theory to the optical lattice system which can be described by the t-J model or the Hubbard model in an harmonic trap. This step is the cornerstone of this project. 2) To calculate the double occupancy at various U and number of atoms and compare the results with the recent experiment where the Mott insulator is observed. This is a test for our theory. We must make sure the theoretical results are consistent with the experimental data before we do further investigation. 3) To calculate the spatial distribution of the antiferromagnetic order in the case where the electron density in the center is around half filling. This may address a longstand issue in high Tc superconductors: whethere the antiferromagnetism can coexist with the superconductivity. 4) To study the phase transition in the system with interaction and number of atoms, and calculate the phase diagram. In the bosonic case, the phase transition are replaced by a smooth crossover because of the inhomogeneity in the system. So we want to check if the fermionic system has similar properties. This is very important for the observation of various phase in the experiments. |
| List of Research Outputs |
| Chen W., Yang K., Zhou Y. and Zhang F.C., Theory for superconductivity in iron pnictides at large Coulomb U limit, Frontiers of Physics in China. Higher Education Press, 2009, 4: 447-454. |
| Chen W., Ma F.J., Lu Z.Y. and Zhang F.C., p junction to probe antiphase s-wave pairing in iron pnictide superconductors, Physical Review Letters. New York, The American Physical Society, 2009, 103: 207001: 1-4. |
| Feng X., Chen W., Gao J., Wang Q.H. and Zhang F.C., Anderson impurity in a helical metal, Physical Review B. New York, The American Physical Society, 2010, 81: 235411: 1-5. |
| Gao J., Chen W., Xie X.C. and Zhang F.C., In-plane noncollinear exchange coupling mediated by helical edge states in quantum spin Hall systems, Physical Review B (Rapid Communications). New York, The American Physical Society, 2009, 80: 241302: 1-4. |
| Yang K.Y., Chen W., Rice T.M. and Zhang F.C., Origin of the checkerboard pattern in scanning tunneling microscopy maps of underdoped cuprate superconductors, Physical Review B. New York, The American Physical Society, 2009, 80: 174505: 1-7. |
| Researcher : Chen X |
| List of Research Outputs |
| Brauer G., Anwand W., Grambole D., Egger W., Sperr P., Beinik I., Wang L., Teichert C., Kuriplach J., Lang J., Zviagin S., Cizmar E., Ling F.C.C., Hsu Y.F., Xi Y., Chen X., Djurisic A. and Skorupa W., Characterization of ZnO nanostructures: A challenge to positron annihilation spectroscopy and other methods, physica status solidi (c). Weinheim, Wiley-VCH Verlag GmbH & Co., 2009, 6: 2556-2560. |
| Chen X., Yip C.T., Fung M.K., Djurisic A. and Chan W.K., GaN-nanowire-based dye-sensitized solar cells, Applied Physics A: Materials Science & Processing. Springer, 2010, 100: 15-19. |
| Chen X., Ng M.C.A., Fang F., Djurisic A., Chan W.K., Tam H.L., Cheah K.W., Fong P.W.K., Lui H.F. and Surya C., The influence of the ZnO seed layer on the ZnO nanorod/GaN LEDs, Journal of the Electrochemical Society. The Electrochemical Society, 2010, 157: H308-H311. |
| Djurisic A., Ng A.M.C. and Chen X., ZnO nanostructures for optoelectronics: Material properties and device applications, Progress in Quantum Electronics. Elsevier Ltd., 2010, 34: 191-259. |
| Researcher : Cheng CC |
| List of Research Outputs |
| Cheng C.C., Positron beam studies of fluorine implanted gallium nitride and aluminium gallium nitride. Hong Kong, The University of Hong Kong, 2009, 1-158. |
| Researcher : Cheng KS |
| Project Title: | Properties of strange stars and their observational appearance |
| Investigator(s): | Cheng KS |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2003 |
| Abstract: |
| To study the emissivity and transport properties of electronmagnetic waves in semi-degenerate and inhomogeneous electron gas of the strange star atmosphere; the thermal emissivity of hot quark surface in electron-positron pairs; to calculate electron-positron pairs more precisely, hopefully with accuracy of ~10% or even higher; to study electromagnetic waves produced by passing the quarks and also the propagation of electromagnetic waves through the electron atmosphere, which is semi-degenerate and inhomogeneous; to study the strange star cooling by taking into account the processes mentioned in (1)-(3). And other processes such as formation of color-flavor locked phase inside the star, chiral symmetry requirement in the boundary, will be included in the cooling calculations; to study the observational consequences of producing strange stars by accretion including how much gravitational and phase transition energy will be released through gravitational and electromagnetic waves. The possible connection between this process and [gamma]-ray bursts will be studied as well. |
| Project Title: | Relativistic collapse of neutron stars: gravitational radiation and gamma-ray emission |
| Investigator(s): | Cheng KS, Suen W.M. |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2006 |
| Abstract: |
| (1) We propose to study the physical processes associated with collapsing neutron stars and aim to predict what gravitational wave signals and gamma-ray spectrum will be emitted from these collapsing neutron star systems. We will study two specific neutron star collapse scenarios. 1. When a neutron star in a low-mass X-ray binary accretes about 0.5 solar masses from its companion; it may undergo a phase-transition induced collapse. The collapsing neutron star may or may not evolve to a black hole; a denser compact object, e.g. a quark star, can be formed. The collapse leads to oscillations and an increase in the speed of rotation. The coupling between rotation and oscillations can produce strong gravitational waves. We will also investigate (non-axisymmetric) dynamical instabilities that may develop in the collapse process, in particular the so-called bar-mode instability. (2) Our preliminary Newtonian results indicate that the gravitational-wave signal sensitively depends on the equation of state used. In this project we will extend our previous Newtonian study to a fully relativistic study. The gravitational waveforms to be determined by the proposed study may be detected by the advanced Laser Interferometric Gravitational Wave Observatory (LIGO II), and our results may be used to put constraints on the underlying equation of state. Shock waves and differential rotation, which eventually will lead to high internal energy, will be developed during the collapse. Intense gamma-rays will be emitted from electron – positron annihilations emitted from the hot surface of the quark star. Our proposed study will allow us to test if the accretion induced phase-transition is a possible mechanism of gamma-ray bursts. 2. The merging of two neutron stars in a neutron star binary will lead to a collapse with high angular momentum. (3) The final object is likely a black hole – accretion disk system. It is well-known that the gravitational wave signals emitted from binary neutron star merger sensitively depend on the angular momentum in the system. In fact, how much matter is in the accretion torus outside the event horizon also sensitively depends on the angular momentum. We will calculate the neutrino emission from this hot degenerate accretion disk; subsequent neutrino – antineutrino annihilation can produce electron/positron jet. Although we may not able to answer the baryon contamination problem, we may be able to tell if such system can provide a powerful enough jet to produce the gamma-ray bursts and subsequent afterglow. If the energy content in the accretion disk is low for a wide range of angular momentum, it will challenge the scenario of neutron star merger as a possible central power engine of short gamma-ray bursts.(4) In summary, the objectives of this project are: • To study the gravitational radiations and gamma-ray emissions from phase-transition induced collapse of neutron stars and the physical processes during the collapse • To study how the inspiral parameters of neutron star – neutron star coalescence affect the gravitational waveforms and the matter distributions in the final black hole – accretion disk system |
| Project Title: | High Energy Emission from the Galactic Black Hole |
| Investigator(s): | Cheng KS |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2007 |
| Abstract: |
| The main goal of this project is to study the high energy emission phenomena from the center of Milky Way and find out the origin of the positron annihilation lines. We propose that the tidal capture of stars by the Galactic black hole is a possible mechanism to produce the observed TeV, GeV and positrons via hadronic collisions. We will study the propagation of relativistic protons ejected by the Black hole during accretion phase and try to explain the differences, e.g. spectral index and spatial distribution, between GeV and TeV photons. We will also study the thermalization process of positrons and calculate the positron annihilation lines via in-flight process and formation of positronium in order to compare model results with the observed data. We will study other possible phenomena related to the capture of stars by supermassive black holes in nearby normal galaxies, e.g. would some EGRET unidentified sources result from this process? and radiation in lower energy bands etc. We will also compare this model prediction with other possible positron production models, especially pulsar models. |
| Project Title: | Radiation emission from pulsars |
| Investigator(s): | Cheng KS |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2008 |
| Abstract: |
| 1) We study the structure of outer gap and how it affects the radiation morphology and spectrum of pulsars. 2) We intend to study various radiation features of canonical pulsars, millisecond pulsars and magnetars in particular in the energy range of GLAST. |
| Project Title: | Pulsar Glitches |
| Investigator(s): | Cheng KS |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 03/2009 |
| Completion Date: | 08/2010 |
| Abstract: |
| We intend to use the observed radio timing data of pulsars to study the internal dynamics of neutron stars, which are also called pulsars because of their regularly pulsating features in electromagnetic radiation. Pulsars are strongly magnetized and rapidly spinning neutron stars. They have masses about our Sun but with magnetic field up to 10^15 gauss and period down to one millisecond. The rapid rotation and strong magnetic field can create the large potential drop in the atmosphere, which consists of charge separated plasma. This electric potential drop can accelerate charged particles to extremely relativistic speed, however they are confined by the strong magnetic field, consequently they are moving in a curve trajectory and hence curvature radiation will be emitted. Due to rotation of the star, we will see pulsating emission when the radiation beam passing through the line of sight. The rotation period of pulsars is known to be extremely regular, in many cases they are even better than the atomic clock. However, we have also observed occassionally that some pulsars exhibit period jumps, which are known pulsar glitches. These phenomena can be explained due to sudden angular momentum transfer between the internal superfluid and normal matter. We believe that the radio timing data of pulsars can provide very important information about the properties of internal superfluid. This is very important to understand why superfluid can be formed in such high density objects and why the temperature of the star is higher than million degree but superfluid can still exist. This superfluid must have very much different properties than the superfluid we found in the earth. |
| Project Title: | Probing the central engine of gamma-ray bursts |
| Investigator(s): | Cheng KS |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2009 |
| Abstract: |
| 1) We study rebrigtening phenomena in afterglows and to see if this feature can provide important information about the environments of GRBs. We want to understand what are the controlling parameters to determine which GRBs have rebrigtening features but others do not. We believe that this feature can provide useful information to constraint the possible models of the central engine of GRBs. 2) We study the multi-wavelengths and long period of afterglows to see if we can obtain the further environmental information and the nature of the central engine of GRBs. 3) We study some possible models of GRB central engine to see how flares or shallow decay can occur in the X-ray afterglows of Swift. |
| Project Title: | The 6th Joint Meeting of Chinese Physicists Worldwide (OCPA6) Short Gamma-ray Burst and phase transition induced collapse |
| Investigator(s): | Cheng KS |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 08/2009 |
| Completion Date: | 08/2009 |
| Abstract: |
| N/A |
| Project Title: | Millisecond pulsars |
| Investigator(s): | Cheng KS |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 01/2010 |
| Abstract: |
| In this project we intend to study the evolution of millisecond pulsars in globular clusters. We expect that our initial findings can be used as input data for GRF grant application. Basically we want to address to the following objectives: (1)What are the most important factors to determine the formation rate of millisecond pulsars in globular clusters? We will examine the density, encourter rate of stars, metallicity, velocity dispersion, age of clusters etc to see how these factor correlate with the number of millisecond pulsars. (2)It is generally believe that Low Mass X-ray Binaries are progenitors of millisecond pulsars. However, the accretion rate of these systems generally consist of high state and low state, in particular toward the late evolution stage the accretion is generally low. How can the millisecond pulsars can maintain its short rotation period against the slow down accretion torque? There are stronge evidence suggests that the accretion appears to stop abruptly, why? (3)It is interesting to study the high energy radiation emission from these group of pulsars. Their surface magnetic field is expected to be different significantly from that of canonical pulsars born from supervona explosion. Millisecond pulsars in globular cluster 47 Tuc seem not to radiate any high energy radiation whereas at least millisecond pulsar, at least M28A, in globular cluster M28 is most likely a gamma-ray emitter. What are the most important factor to determine the high energy emission process? |
| List of Research Outputs |
| Cheng K.S., Yu Y. and Harko T.C., High-redshift gamma-ray bursts: Observational signatures of superconducting cosmic strings?, Physical Review Letters. New York, The American Physical Society, 2010, 104: 241102: 1-4. |
| Cheng K.S., Harko T.C., Huang Y.F., Lin L.M., Suen W.M. and Tian X., Relativistic mass ejecta from phase-transition-induced collapse of neutron stars, Journal of Cosmology and Astroparticle Physics. Bristol, IOP Publishing Limited, 2009, 007: 1-30. |
| Chernyshov D., Cheng K.S., Dogiel V.A., Ko C.M. and Ip W.H., Restrictions on the injection energy of positrons annihilating near the Galactic Centre, Monthly Notices of the Royal Astronomical Society. United Kingdom, Royal Astronomical Society, 2010, 403: 817-825. |
| Dogiel V., Cheng K.S., Chernyshov D., Bamba A., Ichimura A., Inoue H., Ko C.M., Kokubun M., Maeda Y., Mitsuda K. and Yamasaki N.Y., Origin of 6.4 keV line emission from molecular clouds in the galactic center, Publications of the Astronomical Society of Japan. Astronomical Society of Japan, 2009, 61: 901-907. |
| Dogiel V.A., Tatischeff V., Cheng K.S., Chernyshov D., Ko C.M. and Ip W.H., Nuclear interaction gamma-ray lines from the galactic center region, Astronomy & Astrophysics. ESO, 2009, 508: 1-7. |
| Dogiel V.A., Chernyshov D.O., Yuasa T., Prokhorov D., Cheng K.S., Bamba A., Inoue H., Ko C.M., Kokubun M., Maeda Y., Mitsuda K., Nakazawa K. and Yamasaki N.Y., Origin of thermal and non-thermal hard X-ray emission from the galactic center, Publications of the Astronomical Society of Japan. Astronomical Society of Japan, 2009, 61: 1099-1105. |
| Dogiel V.A., Chernyshov D.O., Yuasa T., Cheng K.S., Bamba A., Inoue H., Ko C.M., Kokubun M., Maeda Y., Mitsuda K., Nakazawa K. and Yamasaki N.Y., Particle propagation in the galactic center and spatial distribution of non-thermal X-rays, Publications of the Astronomical Society of Japan. Astronomical Society of Japan, 2009, 61: 1093-1098. |
| Hui C.Y., Cheng K.S. and Taam R.E., Diffuse X-ray emission in globular cluster cores, The Astrophysical Journal. The American Astronomical Society, 2009, 700: 1233-1241. |
| Hui C.Y., Cheng K.S. and Taam R.E., Dynamical formation of millisecond pulsars in globular clusters, The Astrophysical Journal. The American Astronomical Society, 2010, 714: 1149-1154. |
| Kong A.K.H., Hui C.Y. and Cheng K.S., Fermi discovery of gamma-ray emission from the globular cluster Terzan 5, The Astrophysical Journal Letters. The American Astronomical Society, 2010, 712: L36-L39. |
| Kong S., Wong Y.L., Huang Y.F. and Cheng K.S., Variation of microphysics in wind bubbles: An alternative mechanism for explaining the rebrightenings in Gamma-ray burst afterglows, Monthly Notices of the Royal Astronomical Society. United Kingdom, Royal Astronomical Society, 2010, 402: 409-416. |
| Kong S.W., Huang Y.F., Cheng K.S. and Lu T., Modeling the radio and optical/NIR afterglows of GRB 980703: A numerical study, Science in China Series G-Physics, Mechanics & Astronomy. Science in China Press, 2009, 52: 2047-2053. |
| Kovacs Z., Cheng K.S. and Harko T.C., Can stellar mass black holes be quark stars ?, Monthly Notices of the Royal Astronomical Society. United Kingdom, Royal Astronomical Society, 2009, 400: 1632-1642. |
| Kovacs Z., Cheng K.S. and Harko T.C., Electron-positron energy deposition rate from neutrino pair annihilation in the equatorial plane of rapidly rotating neutron and quark stars, Monthly Notices of the Royal Astronomical Society. United Kingdom, Royal Astronomical Society, 2010, 402: 1714-1728. |
| Takata J., Wang Y. and Cheng K.S., Pulsar high energy emissions from outer gap accelerator closed by a magnetic pair-creation process, The Astrophysical Journal. The American Astronomical Society, 2010, 715: 1318-1326. |
| Trepl L., Hui C.Y., Cheng K.S., Takata J., Wang Y., Liu Z.Y. and Wang N., Multiwavelength properties of a new Geminga-like pulsar: PSR J2021+4026, Monthly Notices of the Royal Astronomical Society. United Kingdom, Royal Astronomical Society, 2010, 405: 1339-1348. |
| Wong K.C., Cheng K.S. and Harko T.C., Inflation and late-time acceleration in braneworld cosmological models with varying brane tension, European Physical Journal C. Springer, 2010, 68: 241-253. |
| Yu Y., Cheng K.S. and Cao X.F., The role of newly born magnetars in gamma-ray burst X-ray afterglow emission: Energy injection and internal emission , The Astrophysical Journal. The American Astronomical Society, 2010, 715: 477-484. |
| Researcher : Chernyshov D |
| List of Research Outputs |
| Chernyshov D., Cheng K.S., Dogiel V.A., Ko C.M. and Ip W.H., Restrictions on the injection energy of positrons annihilating near the Galactic Centre, Monthly Notices of the Royal Astronomical Society. United Kingdom, Royal Astronomical Society, 2010, 403: 817-825. |
| Dogiel V.A., Tatischeff V., Cheng K.S., Chernyshov D., Ko C.M. and Ip W.H., Nuclear interaction gamma-ray lines from the galactic center region, Astronomy & Astrophysics. ESO, 2009, 508: 1-7. |
| Researcher : Cheung KY |
| List of Research Outputs |
| Cheung K.Y., Metallopolyyne polymers based bulk heterojunction (BHJ) solar cells. Hong Kong, The University of Hong Kong, 2009, 1-111. |
| Mikroyannidis J.A., Cheung K.Y., Fung M.K. and Djurisic A., Synthesis and photovoltaic properties of novel alternating phenylenevinylene or fluorenevinylene copolymers containing perylene bisimide, Reactive & Functional Polymers. Amsterdam, Elsevier Ltd., 2010, 70: 426-432. |
| Wang X.Z., Wang Q.W., Yan L., Wong W.Y., Cheung K.Y., Ng A., Djurisic A. and Chan W.K., Very-low-bandgap metallopolyynes of platinum with a cyclopentadithiophenone ring for organic solar cells absorbing down to the near-infrared spectral region, Macromolecular Rapid Communications. Weinheim, WILEY-VCH Verlag GmbH & Co. KGaA, 2010, 31: 861-867. |
| Wong W.Y., Chow W.C., Cheung K.Y., Fung M.K., Djurisic A. and Chan W.K., Harvesting solar energy using conjugated metallopolyyne donors containing electron-rich phenothiazine-oligothiophene moieties, Journal of Organometallic Chemistry. Amsterdam, Elsevier B.V., 2009, 694: 2717-2726. |
| Researcher : Cheung KY |
| List of Research Outputs |
| Cheung K.Y., Metallopolyyne polymers based bulk heterojunction (BHJ) solar cells. Hong Kong, The University of Hong Kong, 2009, 1-111. |
| Mikroyannidis J.A., Cheung K.Y., Fung M.K. and Djurisic A., Synthesis and photovoltaic properties of novel alternating phenylenevinylene or fluorenevinylene copolymers containing perylene bisimide, Reactive & Functional Polymers. Amsterdam, Elsevier Ltd., 2010, 70: 426-432. |
| Wang X.Z., Wang Q.W., Yan L., Wong W.Y., Cheung K.Y., Ng A., Djurisic A. and Chan W.K., Very-low-bandgap metallopolyynes of platinum with a cyclopentadithiophenone ring for organic solar cells absorbing down to the near-infrared spectral region, Macromolecular Rapid Communications. Weinheim, WILEY-VCH Verlag GmbH & Co. KGaA, 2010, 31: 861-867. |
| Wong W.Y., Chow W.C., Cheung K.Y., Fung M.K., Djurisic A. and Chan W.K., Harvesting solar energy using conjugated metallopolyyne donors containing electron-rich phenothiazine-oligothiophene moieties, Journal of Organometallic Chemistry. Amsterdam, Elsevier B.V., 2009, 694: 2717-2726. |
| Researcher : Chong SN |
| List of Research Outputs |
| Chong S.N., Three dimensional morphology of the dumbbell nebula and the ring nebula. Hong Kong, The University of Hong Kong, 2009, 1-95. |
| Deguchi S., Nakashima J., Zhang Y., Chong S.N., Koike K. and Kwok S., SiO and H2O maser observations of red supergiants in star clusters embedded in the galactic disk, Publications of the Astronomical Society of Japan. Astronomical Society of Japan, 2010, 62: 391-407. |
| Kwok S., Chong S.N., Hsia C., Zhang Y. and Koning N.A., Discovery of a Multipolar Structure with an Equatorial Disk in NGC 6072, The Astrophysical Journal. 2010, 708: 93-100. |
| Nakashima J., Deguchi S., Imai H., Kwok S., Koning N., Yung H.K.B., Zhang Y. and Chong S.N., Telescope Time of CARMA (Project Title: CO Mapping of the Water Fountain Object IRAS 18286-0959) , Combined Array for Research in Millimeter-wave Astronomy (CARMA). 2010. |
| Nakashima J., Kwok S., Zhang Y., Hsia C., Chong S.N., Yung B.H.K., Koning N. and Deguchi S., Telescope Time of the NRO 45m Telescope (Project Title: 3D Structure of the Helix: Verification of the Bicone Model), Nobeyama Radio Observatory, National Astronomical Observatory of Japan. 2010. |
| Zhang Y., Nakashima J., Kwok S., Chong S.N. and Deguchi S., Telescope Time of the NRO 45m Telescope (Project Title: A Spectral Line Survey in the 7mm Window toward the Highly Evolved Carbon Star CIT 6), Nobeyama Radio Observatory, National Astronomical Observatory of Japan. 2010. |
| Researcher : Chong SN |
| List of Research Outputs |
| Chong S.N., Three dimensional morphology of the dumbbell nebula and the ring nebula. Hong Kong, The University of Hong Kong, 2009, 1-95. |
| Deguchi S., Nakashima J., Zhang Y., Chong S.N., Koike K. and Kwok S., SiO and H2O maser observations of red supergiants in star clusters embedded in the galactic disk, Publications of the Astronomical Society of Japan. Astronomical Society of Japan, 2010, 62: 391-407. |
| Kwok S., Chong S.N., Hsia C., Zhang Y. and Koning N.A., Discovery of a Multipolar Structure with an Equatorial Disk in NGC 6072, The Astrophysical Journal. 2010, 708: 93-100. |
| Nakashima J., Deguchi S., Imai H., Kwok S., Koning N., Yung H.K.B., Zhang Y. and Chong S.N., Telescope Time of CARMA (Project Title: CO Mapping of the Water Fountain Object IRAS 18286-0959) , Combined Array for Research in Millimeter-wave Astronomy (CARMA). 2010. |
| Nakashima J., Kwok S., Zhang Y., Hsia C., Chong S.N., Yung B.H.K., Koning N. and Deguchi S., Telescope Time of the NRO 45m Telescope (Project Title: 3D Structure of the Helix: Verification of the Bicone Model), Nobeyama Radio Observatory, National Astronomical Observatory of Japan. 2010. |
| Zhang Y., Nakashima J., Kwok S., Chong S.N. and Deguchi S., Telescope Time of the NRO 45m Telescope (Project Title: A Spectral Line Survey in the 7mm Window toward the Highly Evolved Carbon Star CIT 6), Nobeyama Radio Observatory, National Astronomical Observatory of Japan. 2010. |
| Researcher : Chow FK |
| List of Research Outputs |
| Chau H.F., Chan H.Y. and Chow F.K., On the critical packet injection rate of a preferential next-nearest neighbor routing traffic model on Barabasi-Albert networks, European Physical Journal B. EDP Sciences, 2009, 72: 641-655. |
| Researcher : Chu R |
| List of Research Outputs |
| Chu R., Li J., Jain J.K. and Shen S.Q., Coherent oscillations and giant edge magnetoresistance in singly connected topological insulators, Physical Review B (Rapid Communications). New York, The American Physical Society, 2009, 80: 081102: 1-4. |
| Jiang Z., Chu R. and Shen S.Q., Electric-field modulation of the number of helical edge states in thin-film semiconductors, Physical Review B. New York, The American Physical Society, 2010, 81: 115322: 1-4. |
| Wang B., Chu R., Wang J. and Guo H., First-principles calculation of chiral current and quantum self-inductance of carbon nanotubes, Physical Review B. New York, The American Physical Society, 2009, 80: 235430: 1-5. |
| Researcher : Cui X |
| Project Title: | An optical study of electronic structures of carbon nanotubes |
| Investigator(s): | Cui X |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 08/2006 |
| Completion Date: | 07/2009 |
| Abstract: |
| (1) To build a comprehensive, nondestructive optical measurement system in order to accomplish micro-Raman characterization, photo induced conductance, photoluminescence and electroluminescence spectroscopy at the single carbon nanotube level. (2) To study the excitonic effect, exciton binding strength, electron-photon coupling, and structure dependence of luminescence spectrum on identified single carbon nanotubes by applying micro-Raman characterization, photo induced conductance, photoluminescence and electroluminescence spectroscopy to single carbon nanotubes.(3) The study will elucidate the optical and electric properties of single nanotubes, and will benefit not only carbon nanotube research but also the entire field of the low dimensional physical sciences and nanotechnology. |
| Project Title: | The Study on dielectric function of individual single-walled carbon nanotubes |
| Investigator(s): | Cui X |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2007 |
| Abstract: |
| To experimentally collect reflectance spectra on individual single walled carbon nanotubes with microscope based, single-molecule-type laser spectroscopic methods. To better understand the electronic band structures and optical properties of single carbon nanotubes. |
| Project Title: | The spin current detection in InGaAs/InAlAs Quantum wells |
| Investigator(s): | Cui X |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2008 |
| Abstract: |
| 1) To explore the spin current related physics in 2DEG system. 2) To develop a method to electrically detect pure spin currents. 3) To explore a new solution to spin current based electronic devices. |
| Project Title: | Quantum capacitance of single walled carbon nanotubes |
| Investigator(s): | Cui X |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 06/2009 |
| Abstract: |
| Many electric and optical behaviors of single walled carbon nanotubes (SWNT) have been well interpreted with single fermoin particle theory, though theoretically 1D electron system can be better described by Luttinger liquid which describes interacting electrons in one dimensional conductors. There have been a few experiments addressing electron correlation in single wall carbon nanotuebs, mainly by low temperature transport measurements. In this application, we propose to study electron-electron interaction in nanotubes by quantitative measurements on the quantum capacitance of individual nanotubes. The dependence of capacitance on SWNT geometric structure (i.e. diameter and chiralities), Fermi level and temperature will be investigated. The measurement of capacitance will be an effective probe to SWNT electronic structure and the electron-electron interaction will be examined. Besides, the study of SWNTs’ capacitance will benefit device physics research especially aiming to fast speed nanotube devices. To the author’s knowledge, quantum capacitance and consequently the interacting parameter g of GEOMETRIC STRUCTURAL IDENTIFIED NANOTUBES has never been obtained, though the recent McEuen’s group reported a quantum capacitance measurement on a semiconducting SWNT. 1. Develop a noval method to obtain the quantum capacitance of individual single walled carbon nanotubes 2. Study the dependence of the capacitance on the SWNT’s geometric structure (i.e. diameter and chiralities) 3. Evaluate the quantum capacitance and the density of states of SWNTs and therefore investigate the factors affecting quantum capacitance 4. Obtain the interacting parameter g in Luttinger liquid model for individual SWNTs |
| Project Title: | The Study of Quantum Capacitance of Single walled Carbon nanotubes |
| Investigator(s): | Cui X |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2009 |
| Abstract: |
| 1) To develop a novel method to obtain the quantum capacitance of individual single walled carbon nanotubes; 2) To study the dependence of the capacitance on the SWNT's geometric structure (i.e. diameters and chiralities); 3) To evaluate the quantum capacitance and the density of states of SWNTs and therefore to investigate the factors affecting quantum capacitance; 4) To obtain the interacting parameter g in Luttinger liquid model for individual SWNTs. |
| List of Research Outputs |
| Cui X., Reflectance Spectra of Individual Metallic Single Walled Carbon Nanotubes, ChinaNano2009. 2009. |
| Dai J., Lu H., Yang C., Shen S.Q., Zhang F.C. and Cui X., Magnetoelectric photocurrent generated by direct interband transitions in InGaAs/InAlAs two-dimensional electron gas, Physical Review Letters. New York, The American Physical Society, 2010, 104: 246601: 1-4. |
| Wang X., Wang J., Zhou M.J., Zhu H.J., Wang H., Cui X., Xiao X.D. and Li Q., CdTe nanorod arrays on ITO: From microstructure to photoelectrical property, Journal of Physical Chemistry C. American Chemical Society, 2009, 113: 16951-16953. |
| Yang C., Dai J., Ge W.K. and Cui X., Determination of the sign of g factors for conduction electrons using time-resolved Kerr rotation, Applied Physics Letters. New York, American Institute of Physics, 2010, 96: 152109: 1-3. |
| Researcher : Dai J |
| List of Research Outputs |
| Dai J., Lu H., Yang C., Shen S.Q., Zhang F.C. and Cui X., Magnetoelectric photocurrent generated by direct interband transitions in InGaAs/InAlAs two-dimensional electron gas, Physical Review Letters. New York, The American Physical Society, 2010, 104: 246601: 1-4. |
| Yang C., Dai J., Ge W.K. and Cui X., Determination of the sign of g factors for conduction electrons using time-resolved Kerr rotation, Applied Physics Letters. New York, American Institute of Physics, 2010, 96: 152109: 1-3. |
| Researcher : Ding G |
| List of Research Outputs |
| Ding G., Ling F.C.C., Anwand W..., Brauer G... and Skorupa W..., Deep level transient spectroscopic study of nitrogen-implanted ZnO single crystal, The 37th International Symposium on Compound Semiconductors, May 31 to June 4 2010, Kagawa, Japan. 2010. |
| Researcher : Djurisic A |
| Project Title: | Antimicrobial nanostructured coatings deposited by low temperature, inexpensive, solution methods |
| Investigator(s): | Djurisic A, Chan WK, Leung FCC |
| Department: | Physics |
| Source(s) of Funding: | Research Fund for the Control of Infectious Diseases - Full Grants |
| Start Date: | 09/2007 |
| Abstract: |
| To develop a protective coating which can be applied to different surfaces to significantly reduce pathogen presence; to develop multifunctional antimicrobial coatings which could be fabricated via low temperature solution processes. |
| Project Title: | Teaching renewable energy in the laboratory |
| Investigator(s): | Djurisic A, Beling CD |
| Department: | Physics |
| Source(s) of Funding: | Run Run Shaw Research and Teaching Endowment Fund - Teaching Grants |
| Start Date: | 09/2007 |
| Abstract: |
| Developing new experiments for teaching basic science concepts of the use of nanotechnology in solar cells Developing methods for interdisciplinary science teaching through laboratory experiments - the students will learn basic principles in physics, chemistry, and environmental science by fabricating and characterizing solar cells based on nanocrystalline TiO2. |
| Project Title: | Light Emitting Diodes Fabricated by Electrochemical Methods |
| Investigator(s): | Djurisic A, Chan WK |
| Department: | Physics |
| Source(s) of Funding: | Innovation and Technology Support Programme (Tier 3) |
| Start Date: | 12/2008 |
| Completion Date: | 11/2009 |
| Abstract: |
| 1. Development of low-cost, novel procedure for doped p- and n-type metal oxide layers. The main light emitting material will be ZnO, deposited by chemical/electrochemical methods. The emission will be tailored by defect engineering (UV, green-yellow, orange) or doping. 2. Improvement in light extraction using photonic crystal structures or textured substrates. Improvement in the light extraction efficiency of 20-50% compared to unmodified substrates is expected. 3. Fabrication of light emitting devices with improved performance using electrodeposition. This will include devices with both p- and n-type layers fabricated by chemical/electrochemical methods, as well as devices with light-emitting layer fabricated by chemical/electrochemical techniques on p-type semiconductor substrates to facilitate integration of this approach with conventional technologies. Prototype devices with at least one emission colour will be fabricated. The target turn-on voltages of the devices will be 5-6 V and 8-10 V (depending on device architecture), and brightness will be improved to a value not less than 0.5 µW/cm2 (microwatt per cm2). |
| Project Title: | Optimization of light-trapping in solar cells |
| Investigator(s): | Djurisic A |
| Department: | Physics |
| Source(s) of Funding: | Small Project Funding |
| Start Date: | 01/2009 |
| Completion Date: | 04/2010 |
| Abstract: |
| Llight trapping to increase absorption and consequently the short circuit current density is a common approach in thin film solar cells. Calculations predict significant enhancement of photocurrent using random textured surfaces [1], periodic structures (with or without mirrors) [2], and photonic crystals [3]. With a few exceptions, the effects of scattering are typically disregarded in the analysis of organic solar cells, even though it has been shown that scattering effects lead to a significant enhancement of the absorbance [2]. Light trapping structures and device designs have been used in inorganic thin films cells [4] and dye-sensitized solar cells [5,6]. However, although unintentionally rough surfaces are sometimes observed in polymer solar cells, the research on the effect of scattering structures has been mostly limited to simulations. Therefore, we propose to fabricate and characterize organic solar cells with textured surfaces to evaluate the effect of scattering on photovoltaic performance. The project objectives are: 1. Fabrication of textured electrode surfaces and study of the effect of feature size and rms roughness on photovoltaic performance. 2. Fabrication of active layer with roughness with lateral feature sizes of the order of magnitude comparable to wavelength. 3. Fabrication of mirrors and/or photonic crystal structures to further enhance the absorption. [1] S. Fahr, C. Rockstuhl, F. Lederer, Appl. Phys. Lett. 92, 171114 (2008) [2] R. Shikler, R. H. Friend, J. Appl. Phys. 102, 013105 (2007) [3] D. Y. Zhou and R. Biswas, J. Appl. Phys, 103, 093102 (2008). [4] R. H. Franken, R. L. Stolk, H. Li, C. H. M. van der Werf, J. K. Rath, R. E. I. Schropp, J. Appl. Phys. 102, 014503 (2007). [5] H. J. Koo, Y. J. Kim, Y. H. Lee, W. I. Lee, K. Kim, N. G. Park, Adv. Mater. 20, 195 (2008). [6] S. Ito, T. N. Murakami, P. Comte, P. Liska, C. Gratzel, M. K. Nazeeruddin, M. Gratzel, Thin Solid Films 516, 4613 (2008) |
| Project Title: | Studies of Fundamental Properties of Nanosurfaces and Selected Applications |
| Investigator(s): | Djurisic A |
| Department: | Physics |
| Source(s) of Funding: | Collaborative Research Fund (CRF) - Group Research Project |
| Start Date: | 06/2009 |
| Abstract: |
| The performance of nanoscale devices is often dominated by their surface properties. For example, surfaces introduce undesired electronic states in electronic and optoelectronic devices constructed from semiconducting nanostructures. By contrast, surface activity should be enhanced in nanostructures used as antibacterial agents. To improve such performance, our aim is to provide quantitative atomic-scale information about nanoscale surfaces. Our project will achieve this by introducing a new methodology; we will intentionally design and fabricate novel and highly-controlled nanoplatforms that allow for the first time detailed determination of surface structure and modeling of their relevant surface properties. |
| Project Title: | 2nd International Conference on Physics of Optical Materials and Devices (ICOM2009) ZnO nanomaterials: optical properties and device applications |
| Investigator(s): | Djurisic A |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 08/2009 |
| Completion Date: | 08/2009 |
| Abstract: |
| N/A |
| Project Title: | Indium and tin oxide-based nanorods/nanowires for photovoltaic applications |
| Investigator(s): | Djurisic A |
| Department: | Physics |
| Source(s) of Funding: | Small Project Funding |
| Start Date: | 01/2010 |
| Abstract: |
| Low cost solar cells are of significant interest due to energy crisis. While solar cells based on organic materials have the potential for low cost production, their efficiency needs to be significantly improved, in particular the charge collection efficiency. The objectives of this proposal are to fabricate different nanostructures based on indium and tin oxides (indium oxide, tin oxide, and/or indium tin oxide) for the purpose of improving the charge collection in organic photovoltaic cells. Thus we propose to: 1. Study the growth of indium oxide, tin oxide, and/or indium tin oxide nanostructures using vapor deposition as well as solution base dmethods such as hydrothermal synthesis and electrodeposition. 2. Study the optical and electronic properties of fabricated nanostructures. 3. Apply these nanostructures in polymer and dye-sensitized solar cells. |
| List of Research Outputs |
| Brauer G., Anwand W., Grambole D., Egger W., Sperr P., Beinik I., Wang L., Teichert C., Kuriplach J., Lang J., Zviagin S., Cizmar E., Ling F.C.C., Hsu Y.F., Xi Y., Chen X., Djurisic A. and Skorupa W., Characterization of ZnO nanostructures: A challenge to positron annihilation spectroscopy and other methods, physica status solidi (c). Weinheim, Wiley-VCH Verlag GmbH & Co., 2009, 6: 2556-2560. |
| Chen X., Yip C.T., Fung M.K., Djurisic A. and Chan W.K., GaN-nanowire-based dye-sensitized solar cells, Applied Physics A: Materials Science & Processing. Springer, 2010, 100: 15-19. |
| Chen X., Ng M.C.A., Fang F., Djurisic A., Chan W.K., Tam H.L., Cheah K.W., Fong P.W.K., Lui H.F. and Surya C., The influence of the ZnO seed layer on the ZnO nanorod/GaN LEDs, Journal of the Electrochemical Society. The Electrochemical Society, 2010, 157: H308-H311. |
| Djurisic A., Xie M.H. and Leung Y.H., Doping of wide band gap nanostructures: ZnO and GaN, In: W. Chen, Doped Nanomaterials and Nanodevices. American Scientific Publishers, 2010, Chapter 4: 101-133. |
| Djurisic A., Ng A.M.C. and Chen X., ZnO nanostructures for optoelectronics: Material properties and device applications, Progress in Quantum Electronics. Elsevier Ltd., 2010, 34: 191-259. |
| Mak S.K., Wong H.L., Leung Q.Y., Tam W.Y., Chan W.K. and Djurisic A., The use of sublimable chlorotricarbonyl bis(phenylimino)acenaphthene rhenium(I) complexes as photosensitizers in bulk-heterojunction photovoltaic devices, Journal of Organometallic Chemistry. ELSEVIER SCIENCE SA, 2009, 694: 2770-2776. |
| Mikroyannidis J.A., Cheung K.Y., Fung M.K. and Djurisic A., Synthesis and photovoltaic properties of novel alternating phenylenevinylene or fluorenevinylene copolymers containing perylene bisimide, Reactive & Functional Polymers. Amsterdam, Elsevier Ltd., 2010, 70: 426-432. |
| Ng M.C.A., Xi Y., Hsu Y.F., Djurisic A., Chan W.K., Gwo S., Tam H.L., Cheah K.W., Fong P.W.K., Lui H.F. and Surya C., GaN/ZnO nanorod light emitting diodes with different emission spectra, Nanotechnology. Bristol, IOP Publishing Limited, 2009, 20: 445201: 1-8. |
| Tong W.Y., Chen H.Y., Djurisic A., Ng A.M.C., Wang H., Gwo S. and Chan W.K., Infrared photoluminescence from α- and β-copper phthalocyanine nanostructures, Optical Materials. Amsterdam, Elsevier B.V., 2010, 32: 924-927. |
| Wang X.Z., Wang Q.W., Yan L., Wong W.Y., Cheung K.Y., Ng A., Djurisic A. and Chan W.K., Very-low-bandgap metallopolyynes of platinum with a cyclopentadithiophenone ring for organic solar cells absorbing down to the near-infrared spectral region, Macromolecular Rapid Communications. Weinheim, WILEY-VCH Verlag GmbH & Co. KGaA, 2010, 31: 861-867. |
| Wong W.Y., Chow W.C., Cheung K.Y., Fung M.K., Djurisic A. and Chan W.K., Harvesting solar energy using conjugated metallopolyyne donors containing electron-rich phenothiazine-oligothiophene moieties, Journal of Organometallic Chemistry. Amsterdam, Elsevier B.V., 2009, 694: 2717-2726. |
| Wong W.Y., Leung T.Y., Djurisic A. and Leung K.M.Y., Toxicities of nano zinc oxide to five marine organisms: influences of aggregate size and ion solubility, Analytical and Bioanalytical Chemistry. Springer, 2010, 396: 609-618. |
| Wong W.Y., Leung T.Y., Djurisic A. and Leung K.M.Y., Toxicities of nano zinc-oxide to five marine organisms: influences of aggregate size and ion solubility, the SETAC Asia/Pacific 2010 Meeting, held during 4-7 June 2010 at Guangzhou, China. 2010. |
| Xi Y., Huang B., Djurisic A., Chan M.N., Leung F.C.C., Chan W.K. and Au D.T.W., Electrodeposition for antibacterial nickel-oxide-based coatings, Thin Solid Films. Amsterdam, Elsevier B.V., 2009, 517: 6527-6530. |
| Zhong Y.C., Wong K.S., Djurisic A. and Hsu Y.F., Study of optical transitions in an individual ZnO tetrapod using two-photon photoluminescence excitation spectrum, Applied Physics B: Lasers and Optics. Springer, 2009, 97: 125-128. |
| Researcher : Fan J |
| List of Research Outputs |
| Fan J., Zhu C., Fung S.H.Y., Zhong Y.C., Wong K.S., Xie Z., Brauer G., Anwand W., Skorupa W., To C.K., Yang B., Beling C.D. and Ling F.C.C., Arsenic doped p-type zinc oxide films grown by radio frequency magnetron sputtering, Journal of Applied Physics. New York, American Institute of Physics, 2009, 106: 073709: 1-6. |
| Researcher : Fang F |
| List of Research Outputs |
| Chen X., Ng M.C.A., Fang F., Djurisic A., Chan W.K., Tam H.L., Cheah K.W., Fong P.W.K., Lui H.F. and Surya C., The influence of the ZnO seed layer on the ZnO nanorod/GaN LEDs, Journal of the Electrochemical Society. The Electrochemical Society, 2010, 157: H308-H311. |
| Researcher : Feng X |
| List of Research Outputs |
| Feng X., Chen W., Gao J., Wang Q.H. and Zhang F.C., Anderson impurity in a helical metal, Physical Review B. New York, The American Physical Society, 2010, 81: 235411: 1-5. |
| Researcher : Fu X |
| List of Research Outputs |
| Liu C., Fu X., Chen G., Tang L.H., Hwa T. and Huang J., Formation of novel pattern by programming cell motility, 2010 Hong Kong Inter-University Biochemistry Postgraduate Symposium, CUHK, Hong Kong, 15 May,. 2010. |
| Researcher : Fung FCH |
| List of Research Outputs |
| Fung F.C.H., Ma X.F. and Chau H.F., Practical issues in quantum-key-distribution postprocessing, Physical Review A. New York, The American Physical Society, 2010, 81: 012318: 1-15. |
| Researcher : Fung MK |
| List of Research Outputs |
| Chen X., Yip C.T., Fung M.K., Djurisic A. and Chan W.K., GaN-nanowire-based dye-sensitized solar cells, Applied Physics A: Materials Science & Processing. Springer, 2010, 100: 15-19. |
| Mikroyannidis J.A., Cheung K.Y., Fung M.K. and Djurisic A., Synthesis and photovoltaic properties of novel alternating phenylenevinylene or fluorenevinylene copolymers containing perylene bisimide, Reactive & Functional Polymers. Amsterdam, Elsevier Ltd., 2010, 70: 426-432. |
| Wong W.Y., Chow W.C., Cheung K.Y., Fung M.K., Djurisic A. and Chan W.K., Harvesting solar energy using conjugated metallopolyyne donors containing electron-rich phenothiazine-oligothiophene moieties, Journal of Organometallic Chemistry. Amsterdam, Elsevier B.V., 2009, 694: 2717-2726. |
| Researcher : Fung SHY |
| List of Research Outputs |
| Cen Z.H., Chen T.P., Ding L., Liu Y., Liu Z., Yang M., Wong J.I., Goh W.P., Zhu F.R. and Fung S.H.Y., Quenching and reactivation of electroluminescence by charge trapping and detrapping in Si-implanted silicon nitride thin film, IEEE Transactions on Electron Devices. IEEE, 2009, 56: 3212-3217. |
| Fan J., Zhu C., Fung S.H.Y., Zhong Y.C., Wong K.S., Xie Z., Brauer G., Anwand W., Skorupa W., To C.K., Yang B., Beling C.D. and Ling F.C.C., Arsenic doped p-type zinc oxide films grown by radio frequency magnetron sputtering, Journal of Applied Physics. New York, American Institute of Physics, 2009, 106: 073709: 1-6. |
| Yang M., Chen T.P., Ding L., Liu Y., Zhu F.R. and Fung S.H.Y., Capacitance switching in SiO2 thin film embedded with Ge nanocrystals caused by ultraviolet illumination, Applied Physics Letters. New York, American Institute of Physics, 2009, 95: 091111: 1-3. |
| Zhu W., Chen T.P., Liu Y., Yang M., Zhang S., Zhang W.L. and Fung S.H.Y., Charging-induced changes in reverse current-voltage characteristics of Al/Al-rich Al2O3/p-Si diodes, IEEE Transactions on Electron Devices. IEEE, 2009, 56: 2060-2064. |
| Zhu W., Chen T.P., Liu Z., Yang M., Liu Y. and Fung S.H.Y., Resistive switching in aluminum/anodized aluminum film structure without forming process, Journal of Applied Physics. New York, American Institute of Physics, 2009, 106: 093706: 1-4. |
| Researcher : Gao J |
| Project Title: | Opto-electric response in heteroepitaxial junctions composed of transition metal perovskites |
| Investigator(s): | Gao J |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 01/2007 |
| Completion Date: | 12/2009 |
| Abstract: |
| (1) To study the opto-electronic response of heteroepitaxial p-n junctions of perovskite manganites. Heteroepitaxial junctions with a well-defined interface are essential for the proposed study. A good control over the crystal perfection, epitaxial orientation, as well as a clear interface at atomic level in multiplayer structures will be pursued. The photo-electronic interaction and influence of optical irradiation on the I-V characteristics and transport will be studied with different wavelengths and light intensity. This research aims at obtaining dynamic light control of electrical transport in various hetero-structures. (2) To investigate the electronic states and boundary resistance under an optical or e-field excitation. This study can explore how the applied optical or electric field affects the properties of the material in hoping to shed light on the physical mechanisms, which are difficult to understand using conventional research scheme. Our recent study has shown that a current with a high density can induce a giant ER in the ABO3 films. With the incorporation of optical excitation into the experiment, free carriers can be excited in the materials and, likely, the MI transition will be influenced. Our research will be focused on the dynamical process of the way that electrons are excited and combined with holes and how the photon-generated electrons interact with Mn ions. The impurity states will also be investigated. (3) To explore the effect of the strain on the electroresistance (ER) and photocarrier injection. Films with different thicknesses will be made to study the strain effect. It has been known that lattice strain can greatly affect the Curie temperature and the phase transition. Recently we also found that the strain can greatly influence the ER effect induced by currents. It could be associated with the multi-phases coexistence in R1-xAxMnO3, though the physical mechanism has not fully understood yet. The optical excitation is likely to influence the MI transition and introduce some metastable states as well. Thus the effect of lattice strain on the optical process is of great interest. |
| Project Title: | Field effect in epitaxial thin films of perovskite manganites based on simple planar field effect configurations |
| Investigator(s): | Gao J |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 01/2008 |
| Abstract: |
| Optimization of the monolayer EFC: A good control over a wide range of the fields and field gradient in the formed EFC is essential for the proposed project. This research aims at developing a simple, efficient, and highly reliable planar EFC based on monolayer of R1-xAxMnO3 materials. Different designs will be developed to match various peroviskite manganites, which may have rather different behavior. Study of the impact of e-fields on the transport in various systems: Applying our planar EFC to various perovskite manganites, the e-field modulation on their IM phase transition and its influence on the transport will be investigated. This part of study can clarify how the applied e-field interacts with the induced polarization and affects the nature of the transport in this class of materials. Our goal is to explore the possibility to easily control the IM-phase transition and other properties in these systems. Investigation on the e-field induced electroresistance (ER): Research effort will also be made to the ER effect introduced by e-fields. The results will be compared with the giant ER induced by a high current. Understanding of the fundamental mechanisms of the obtained experimental observations will be pursued, especially the correlations between metastable states created by external fields and the coexistence of multiphases in different systems. |
| Project Title: | An investigation on novel multiferroic materials |
| Investigator(s): | Gao J |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 06/2008 |
| Completion Date: | 11/2009 |
| Abstract: |
| Multiferroics are advanced novel functional materials which show rich variety of physical properties like ferroelectric, ferromagnetic, and/or ferroelastic in a single system. Because of the strong coupling between magnetic and electric polarization, controllable switching among different states provides possibility for novel microelectronic devices like information memory elements. Moreover, combining both inductive and capacitive natures, multi-ferroelectrics is of significant merits in microwave technology and wideband electromagnetic detectors. Therefore the search of novel multiferroic materials with superior magnetic and electric properties has triggered intense research interests recently. It is known that the strong ferroelectric and ferromagnetic could not coexist in one system due to the center symmetric structure needed for magnetic states and asymmetric feature of ferrodielectrics.[1, 2] Thus the electric/magnetic coupling in usual materials is rather weak and the magneto-ferroelectric system is seldom seen. To date the reported magneto-ferroelectrics are rather limited. Most of them are distorted perovskite oxides like AMnO3 (A=Bi, Y, Ho, Tb), BiFeO3, BiCrO3.[3-10] Fiebig et al recently observed coexistence of ferroelectric domain and ferromagnetic domain in YMnO3.[11] Subsequently, Hur et al successfully modulated electric polarization by a magnetic field in TbMnO3.[12] It was found that a periodic magnetic field could yield to reversible and repeatable periodic conversion of the polarization, demonstrating the feasibility of ferroelectric memory effect which is magnetically tunable. However, in these materials the temperature for magnetic ordering is relative low (The Tc for BiMnO3 is 105 K, the Neel temperature for YMnO3, HoMnO3, and TaMnO3 is 80 K, 75 K, and 40 K, respectively), leading to a lower coupling temperature. The modulation field required is very high, typically around several Tesla. Recent attempt to utilize physical or chemical synthesis of ferroelectric/ferromagnetic composite has made an exciting progress. Combining strong ferromagnetic compounds and ferroelectrics on nano/submicron scale may retain coexistence of ferroelectric/magnetic states and gain a strong ferroelectric/magnetic coupling although the properties of such a composite could be further improved.[13] Another potential technique to obtain strong ferroelectric/magnetic composite is to construct superlattice structures. It may not only restrain symmetric centers, enable coexistence of ferromagnetic/ferroelectric ordering, but also gain ferromagnetic/electric coupling through the inter-layer coupling. Whereas, by changing the layer thickness the orbital and charge disorder could be controlled, hence affect the symmetry of the system.[14] The state of the art of thin film technology enable us to well control the growth of artificial structure of ferromagnetic/electrics on atomic, nano, or micro scale. Recent report of epitaxial BiMnO3 films on silicon revealed high polarization and piezoelectric coefficient (~45 C/cm2 and ~60 pm/V) as well as magnetization (150 emu/cc), highlighting potential application of thin film technology in developing novel functional materials.[8] In this project, we propose a systematic investigation on the controllable synthesis of multiferroic composite using the state of the art of thin film technology, and on the correlated ferromagnetic/ferroelectric coupling effect. The motivation of the research aims at the possible functional novel device applications. We intend to use substrates with different lattice and orientation and laser molecular beam epitaxial technique to gain ferroelectric/ferromagnetic composite or artificial superlattice structures. We will study the influence of electric fields in changing the ordering and polarization of the micro-domain of ferroelectric layers on magnetic microstructures due to the strong ferroelectric/magnetic coupling; as well as the effect of a magnetic field on ferroelectric states and domain structures, especially the related dynamics. Our goal is to explore the conditions and nature of the coexistence of ferroelectric/ferromagnetic states, and the feasibility to modulate the micro-domain and macro properties. Hence to develop novel and advanced multiferroic materials and devices. References [1] N. A. Hill, J. Phys. Chem. B, 104, 6694 (2000) [2] J. Wang et al., Science 299, 1719 (2003) [3] T. Kyomen et al., Ferroelectrics 264, 1881 (2001) [4] T. Kimura et al., Phys. Rev. B 67, 180401 (2003) [5] M. Fiebig et al., Nature 419, 818 (2002) [6] B. V. Aken et al., Nature Materials 3, 164(2004) [7] T. Kimura et al., Nature 426, 55 (2003) [8] J. Wang et al., Appl. Phys. Lett. 85, 2574 (2004) [9] Y. P. Wang et al., Appl. Phys. Lett. 84, 1731 (2004) [10] T. Goto et al., Phys. Rev. Lett. 92, 257201 (2004) [11] M. Fiebig et al. Nature 419, 818-820 (2002) [12] N. Hur et al, Nature 429, 392-395(2004) [13] H. Zheng et al. Science 303, 661(2004) [14] D. V. Efremov et al. Nature Mater 3, 853(2004) |
| Project Title: | Field effect in hetero-composites integrated with various perovskite and ferroelectric oxides |
| Investigator(s): | Gao J |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 04/2009 |
| Abstract: |
| In this project, we propose an investigation on the hetero-composites made of manganite perovskites like CMR and ferroelectric oxides. The study of heteroepitaxial structures combining different functional materials is motivated by the potential to construct novel functional devices for various applications and the boosted interest for unusual effects of such composed heterojunctions differing substantially from those in corresponding bulk materials. Such functional composite heterojunctions can exhibit exceptional mechanical, magnetic and electronic properties that have not been observed in their bulk counterparts alone. The main objectives: 1. To prepare hetero-composites using various perovskite oxides and ferroelectrics. The main task of this research is to develop heterostructures integrated by various R1-xAxMnO3 manganites and ferroelectric oxides. Various manganites will be integrated with selected ferroelectric oxides by pulse laser deposition and/or sputtering. 2. To explore the feasibility to employ e-field to influence the properties in the grown perovskite layer. The e-field modulation on the IM phase transition and its influence on the transport will be investigated. Our goal is to explore the feasibility to well controlled the electromagnetic properties in the grown manganites. 3. To obtain some preliminary results for applying external funding. On the basis of this research, we will seek for external funding for further investigation alone this direction. |
| Project Title: | Controlled deformation and tunable electromagnetic properties by electrostrictive/piezoelectric effect in manganite/ferroelectrics heterostructures |
| Investigator(s): | Gao J |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 01/2010 |
| Abstract: |
| 1) Fabrication of hetero-epitaxial structures by integrating various R1-xAxMnO3 compounds with piezoelectric perovskites. 2) To clarify the piezoelectric properties of the employed ferroelectrics near the MI transition or the Curie point. 3) To study the modulation on electromagnetic properties of the manganites by controlled deformation, and to understand the related physical mechanisms. |
| List of Research Outputs |
| Feng X., Chen W., Gao J., Wang Q.H. and Zhang F.C., Anderson impurity in a helical metal, Physical Review B. New York, The American Physical Society, 2010, 81: 235411: 1-5. |
| Fu M., Xie Q.Y., Gu M.Q., Zhang Y.M., Wu X.S., Pan F.M., Chen X.C., Wu L.H., Pan G.Q. and Gao J., Substrate effects on the ordering nanostructure for La2/3Ca1/3MnO3 ultrathin films, Journal of Crystal Growth. Amsterdam, Elsevier B.V., 2010, 312: 1617-1621. |
| Gao J., Hu F. and Liu H., Field effects in thin films of manganites using a planar field effect configuration, Journal of Superconductivity and Novel Magnetism. Springer, 2010, 23: 855-857. |
| Gao J., Chen W., Xie X.C. and Zhang F.C., In-plane noncollinear exchange coupling mediated by helical edge states in quantum spin Hall systems, Physical Review B (Rapid Communications). New York, The American Physical Society, 2009, 80: 241302: 1-4. |
| Hao J.H. and Gao J., Method for epitaxial growth of (110)-oriented SrTiO3 thin films on silicon without template, United States Patent. 2010, US 7,718,516 B2. |
| Luo Z. and Gao J., Anomalous temperature and magnetic field dependences of current-voltage characteristics in Pr0.6Ca0.4MnO3/Nb-doped SrTiO3 heterojunctions, Journal of Physics D: Applied Physics. Bristol, IOP Publishing Limited, 2010, 43: 175003: 1-6. |
| Tan W.S., Wu H.P., Deng K.M., Wu X.S., Jia Q.J. and Gao J., Studies on strain relaxation and in-plane orientation of La0.7Ca0.3MnO3 film by grazing incidence X-ray diffraction, Journal of Alloys and Compounds. Amsterdam, Elsevier B.V., 2010, 491: 545-549. |
| Wang J., Gao J. and Wang L., Resistance steps and asymmetric conduction induced by currents in La0.8Ca0.2MnO3 films, IEEE Transactions on Magnetics. IEEE, 2010, 46: 1-8. |
| Wang Z., Yu G.L., Qiu L., Wu X.S., Wang L. and Gao J., Magnetically tunable properties related with carriers density in self-doped La1−xMnO3/y wt %Nb-SrTiO3 heteroepitaxial junctions, Journal of Applied Physics. New York, American Institute of Physics, 2010, 107: 09C704: 1-3. |
| Zhang A.M., Cai H.L., Wu X.S., Wang Z.H., Gao J. and Jia Q.J., Strain effect in cation disorder manganite films, Journal of Superconductivity and Novel Magnetism. Springer, 2010, 23: 867-870. |
| Researcher : Gao J |
| List of Research Outputs |
| Feng X., Chen W., Gao J., Wang Q.H. and Zhang F.C., Anderson impurity in a helical metal, Physical Review B. New York, The American Physical Society, 2010, 81: 235411: 1-5. |
| Fu M., Xie Q.Y., Gu M.Q., Zhang Y.M., Wu X.S., Pan F.M., Chen X.C., Wu L.H., Pan G.Q. and Gao J., Substrate effects on the ordering nanostructure for La2/3Ca1/3MnO3 ultrathin films, Journal of Crystal Growth. Amsterdam, Elsevier B.V., 2010, 312: 1617-1621. |
| Gao J., Hu F. and Liu H., Field effects in thin films of manganites using a planar field effect configuration, Journal of Superconductivity and Novel Magnetism. Springer, 2010, 23: 855-857. |
| Gao J., Chen W., Xie X.C. and Zhang F.C., In-plane noncollinear exchange coupling mediated by helical edge states in quantum spin Hall systems, Physical Review B (Rapid Communications). New York, The American Physical Society, 2009, 80: 241302: 1-4. |
| Hao J.H. and Gao J., Method for epitaxial growth of (110)-oriented SrTiO3 thin films on silicon without template, United States Patent. 2010, US 7,718,516 B2. |
| Luo Z. and Gao J., Anomalous temperature and magnetic field dependences of current-voltage characteristics in Pr0.6Ca0.4MnO3/Nb-doped SrTiO3 heterojunctions, Journal of Physics D: Applied Physics. Bristol, IOP Publishing Limited, 2010, 43: 175003: 1-6. |
| Tan W.S., Wu H.P., Deng K.M., Wu X.S., Jia Q.J. and Gao J., Studies on strain relaxation and in-plane orientation of La0.7Ca0.3MnO3 film by grazing incidence X-ray diffraction, Journal of Alloys and Compounds. Amsterdam, Elsevier B.V., 2010, 491: 545-549. |
| Wang J., Gao J. and Wang L., Resistance steps and asymmetric conduction induced by currents in La0.8Ca0.2MnO3 films, IEEE Transactions on Magnetics. IEEE, 2010, 46: 1-8. |
| Wang Z., Yu G.L., Qiu L., Wu X.S., Wang L. and Gao J., Magnetically tunable properties related with carriers density in self-doped La1−xMnO3/y wt %Nb-SrTiO3 heteroepitaxial junctions, Journal of Applied Physics. New York, American Institute of Physics, 2010, 107: 09C704: 1-3. |
| Zhang A.M., Cai H.L., Wu X.S., Wang Z.H., Gao J. and Jia Q.J., Strain effect in cation disorder manganite films, Journal of Superconductivity and Novel Magnetism. Springer, 2010, 23: 867-870. |
| Researcher : Hao J |
| Project Title: | Dielectric properties in novel perovskite oxide thin films |
| Investigator(s): | Hao JH |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 12/2004 |
| Abstract: |
| Objective of the research proposal: Design and synthesis of novel functional oxides with unusual and promising dielectric properties. Investigation of processing effects on the structural and dielectric properties of thin films. Searching and understanding of some possible new phenomena in novel perovskite oxide thin films. The key issue is to investigate how the preparation parameters of perovskite oxide thin film affect their dielectric properties. The key problem is interfacial effects between novel perovskite oxides and various substrates. In the proposed investigation, the growth of epitaxial thin film with full control will be carried out. Various structural, dielectric and optical characterizations will be employed. |
| Researcher : Hao JH |
| Project Title: | Dielectric properties in novel perovskite oxide thin films |
| Investigator(s): | Hao JH |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 12/2004 |
| Abstract: |
| Objective of the research proposal: Design and synthesis of novel functional oxides with unusual and promising dielectric properties. Investigation of processing effects on the structural and dielectric properties of thin films. Searching and understanding of some possible new phenomena in novel perovskite oxide thin films. The key issue is to investigate how the preparation parameters of perovskite oxide thin film affect their dielectric properties. The key problem is interfacial effects between novel perovskite oxides and various substrates. In the proposed investigation, the growth of epitaxial thin film with full control will be carried out. Various structural, dielectric and optical characterizations will be employed. |
| Researcher : Harko TC |
| Project Title: | Eleventh Marcel Grossmann Meeting on General Relativity Can Strange Stars be Distinguished from Neutron Stars? |
| Investigator(s): | Harko TC |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 07/2006 |
| Abstract: |
| N/A |
| Project Title: | High energy radiation, accretion and cooling of strange stars |
| Investigator(s): | Harko TC, Cheng KS |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2007 |
| Abstract: |
| 1) Generation and propagation of radiation in the electrosphere. The thermal radiation from the inner parts of the electrosphere is strongly suppressed if the surface of the strange star (T_s) is less that 10^9K due to the extremely high plasma frequency. However, electron-electron bremsstrahlung radiation emission can take place in the outer parts of the electron layer and thus the electrosphere is a source of X-ray radiation, which may be observable by a distant observer. Because of its specific and unique spectrum, this radiation could become the main observational signature for a bare strange star. We will study the emissivity and spectrum of the radiation generated in the electrosphere, by considering the effects of the degeneracy of the electron gas. 2) Gas accretion onto bare strange stars and surface heating. Although bare strange stars cool extremely rapidly, they could be observed if their surface is reheated by accretion of gas. At present, the process of gas accretion onto strange stars and their reheating is poorly studied. This process differs significantly from the gas accretion onto neutron stars. One of its specific features is a very high heat conductivity of strange quark matter at the stellar surface. Therefore, an essential part of the energy delivered by the gas accretion onto the surface is transferred inside the star. We are planning to study the gas accretion onto bare strange stars. This may hopefully lead to discovery of effects that could help to discriminate bare strange stars and neutron stars. 3) Thermal evolution of strange stars. The thermal evolution is another observational signature to differentiate bare strange stars from neutron stars. In addition to the internal neutrino emission, the surface radiation plays a crucial role in determining the cooling of strange stars, especially at low temperature. We will use the results obtained in the objective (1) to study the thermal evolution of strange stars. We will also investigate the thermal evolution of the accreting strange stars. In particular if the accretion flow is not steady, the thermal radiation from strange stars will be drastically different from those of neutron stars due to the effects mentioned in the objective (2). |
| Project Title: | Brane world cosmology: post-inflationary reheating and gravitational lensing |
| Investigator(s): | Harko TC, Amara A, Cheng KS |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 10/2008 |
| Abstract: |
| 1) We will investigate the possibility that dark matter is the result of the matter exchange between a higher-dimensional space-time (the bulk) and our four-dimensional universe. 2) We will consider the possibility that the dark energy is the result of bulk-brane energy exchange during the post-inflationary reheating phase, and we will study the cosmological/observational implications of this hypothesis. 3) We will study and obtain the optimal strong lensing survey configurations that will allow us to distinguish between brane world models, with bulk-brane energy exchange, and the standard cosmological constant model. |
| Project Title: | Distinguishing stellar mass black holes from exotic compact objects |
| Investigator(s): | Harko TC, Cheng KS |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 01/2009 |
| Completion Date: | 06/2010 |
| Abstract: |
| The main goal of this project is to find some distinctive signatures that could clearly differentiate between standard black holes, as predicted by the theory of general relativity, and classes of astrophysical objects formed from different types of exotic matter like bosons stars, Bose-Einstein condensed matter, quark stars etc., which have several properties like, for example, mass, lack of a distinct surface, or a totally absorbing surface, very similar to those of the standard black holes. There are important observational evidences for massive black holes, like the intermediate-mass black holes (which can be found in the center of globular clusters) and the supermassive black holes in the center of the Milky Way and of the active galaxies. However, recent observations have also shown the existence of the so-called stellar mass black holes, which have been observed in close binary systems in which transfer of matter from a companion star to the black hole occurs. The energy released in the fall heats up the matter to temperatures of several hundred million degrees, and it is radiated in X-rays. The black hole therefore is observable in X-rays, whereas the companion star can be observed with optical telescopes. The energy released for black holes and neutron stars is of the same order of magnitude. Therefore black holes and neutron stars are often difficult to distinguish. Very intriguingly, recent observations have provided clear evidence for the existence of several stellar mass black holes, like, for example, XTE J1650-500, with a mass of 3.8 solar masses, GRO J0422+32 with a mass between 3-5 solar masses, GRO J1655-40 with a mass of around 6 solar masses etc. Since many types of compact objects formed from so called exotic matter (boson stars, quarks stars, condensed stars etc.) have properties similar to the standard black holes, distinguishing between all these classes of compact object is fundamental for contemporary astronomy. The main objectives of the present project are as follows: 1) To study the mass function of different type of compact objects formed from exotic matter and determine the maximum mass such objects can achieve, and the corresponding physical conditions under which this maximum mass can exist. 2) To study the distinctive observational features (energy flux, temperature distribution and equilibrium spectrum) of the thin accretion disks formed around stellar mass black holes and exotic stars with the same mass. 3) To study specific emission lines (like the iron K alpha line) from the accretion disk, and use them to clearly distinguish between black holes and other type of objects. |
| Project Title: | 12th Marcel Grossman Meeting on General Relativity Can stellar mass black holes be quark stars? |
| Investigator(s): | Harko TC |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 07/2009 |
| Completion Date: | 07/2009 |
| Abstract: |
| N/A |
| Project Title: | Wormholes in brane world models |
| Investigator(s): | Harko TC, Cheng KS |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 01/2010 |
| Abstract: |
| The main goal of this project is to study static and time dependent solutions of 5-dimensional Kaluza-Klein gravity and to generate several classes of static, spherically symmetric spacetimes, which are analytic solutions of the field equations. These solutions will be used to construct traversable wormhole geometries in the context of the brane world models. |
| List of Research Outputs |
| Cheng K.S., Yu Y. and Harko T.C., High-redshift gamma-ray bursts: Observational signatures of superconducting cosmic strings?, Physical Review Letters. New York, The American Physical Society, 2010, 104: 241102: 1-4. |
| Cheng K.S., Harko T.C., Huang Y.F., Lin L.M., Suen W.M. and Tian X., Relativistic mass ejecta from phase-transition-induced collapse of neutron stars, Journal of Cosmology and Astroparticle Physics. Bristol, IOP Publishing Limited, 2009, 007: 1-30. |
| Harko T.C., Kovacs Z. and Lobo F.S.N., Can accretion disk properties distinguish gravastars from black holes?, Classical and Quantum Gravity. Bristol, IOP Publishing Limited, 2009, 26: 215006: 1-21. |
| Harko T.C., Matter accretion by brane-world black holes, Journal of the Korean Physical Society. Seoul, Korean Physical Society, 2009, 54: 2583-2594. |
| Harko T.C., Kovacs Z. and Lobo F.S.N., Testing Horava-Lifshitz gravity using thin accretion disk properties, Physical Review D. New York, The American Physical Society, 2009, 80: 044021: 1-7. |
| Kahil M.E. and Harko T.C., Is dark matter an extra-dimensional effect?, Modern Physics Letters A. World Scientific, 2009, 24: 667-682. |
| Kovacs Z., Cheng K.S. and Harko T.C., Can stellar mass black holes be quark stars ?, Monthly Notices of the Royal Astronomical Society. United Kingdom, Royal Astronomical Society, 2009, 400: 1632-1642. |
| Kovacs Z., Cheng K.S. and Harko T.C., Electron-positron energy deposition rate from neutrino pair annihilation in the equatorial plane of rapidly rotating neutron and quark stars, Monthly Notices of the Royal Astronomical Society. United Kingdom, Royal Astronomical Society, 2010, 402: 1714-1728. |
| Wong K.C., Cheng K.S. and Harko T.C., Inflation and late-time acceleration in braneworld cosmological models with varying brane tension, European Physical Journal C. Springer, 2010, 68: 241-253. |
| Researcher : He G |
| List of Research Outputs |
| He G. and Wang Z.D., Single qubit quantum secret sharing with improved security, Quantum Information & Computation. Rinton Press, Inc, 2010, 10: 28-40. |
| Researcher : Hsia C |
| List of Research Outputs |
| Hsia C. and Nakashima J., Telescope Time of Lulin 40 cm Telescope (Project Title: Photometric monitoring for an unique nova V407 Cyg), Lulin Observatory. 2010. |
| Hsia C. and Li J.Z., The Ha halo distribution of 10 nearby planetary nebulae based on the SHASSA imaging data, The Journal of Taipei Astronomical Museum. 2010, 7: 9-23. |
| Kwok S., Chong S.N., Hsia C., Zhang Y. and Koning N.A., Discovery of a Multipolar Structure with an Equatorial Disk in NGC 6072, The Astrophysical Journal. 2010, 708: 93-100. |
| Lin Z.Y., Lin H.C., Ye Q.Z., Lin C.S., Lara L.M., Ip W.H., Hsia C., Hsiao H.Y. and Lin C.H., The observations of Comet C/2007 N3 (Lulin) from SLT at Lulin Observatory, The Journal of Taipei Astronomical Museum. 2010, 7: 1-8. |
| Nakashima J., Kwok S., Zhang Y., Hsia C., Chong S.N., Yung B.H.K., Koning N. and Deguchi S., Telescope Time of the NRO 45m Telescope (Project Title: 3D Structure of the Helix: Verification of the Bicone Model), Nobeyama Radio Observatory, National Astronomical Observatory of Japan. 2010. |
| Researcher : Hsu YF |
| List of Research Outputs |
| Brauer G., Anwand W., Grambole D., Egger W., Sperr P., Beinik I., Wang L., Teichert C., Kuriplach J., Lang J., Zviagin S., Cizmar E., Ling F.C.C., Hsu Y.F., Xi Y., Chen X., Djurisic A. and Skorupa W., Characterization of ZnO nanostructures: A challenge to positron annihilation spectroscopy and other methods, physica status solidi (c). Weinheim, Wiley-VCH Verlag GmbH & Co., 2009, 6: 2556-2560. |
| Ng M.C.A., Xi Y., Hsu Y.F., Djurisic A., Chan W.K., Gwo S., Tam H.L., Cheah K.W., Fong P.W.K., Lui H.F. and Surya C., GaN/ZnO nanorod light emitting diodes with different emission spectra, Nanotechnology. Bristol, IOP Publishing Limited, 2009, 20: 445201: 1-8. |
| Zhong Y.C., Wong K.S., Djurisic A. and Hsu Y.F., Study of optical transitions in an individual ZnO tetrapod using two-photon photoluminescence excitation spectrum, Applied Physics B: Lasers and Optics. Springer, 2009, 97: 125-128. |
| Researcher : Hu F |
| List of Research Outputs |
| Gao J., Hu F. and Liu H., Field effects in thin films of manganites using a planar field effect configuration, Journal of Superconductivity and Novel Magnetism. Springer, 2010, 23: 855-857. |
| Researcher : Huang B |
| List of Research Outputs |
| Xi Y., Huang B., Djurisic A., Chan M.N., Leung F.C.C., Chan W.K. and Au D.T.W., Electrodeposition for antibacterial nickel-oxide-based coatings, Thin Solid Films. Amsterdam, Elsevier B.V., 2009, 517: 6527-6530. |
| Researcher : Hui CY |
| List of Research Outputs |
| Hui C.Y., Cheng K.S. and Taam R.E., Dynamical formation of millisecond pulsars in globular clusters, The Astrophysical Journal. The American Astronomical Society, 2010, 714: 1149-1154. |
| Researcher : Hwa TT |
| List of Research Outputs |
| Liu C., Fu X.F., Ren X.J., Chen G.H., Tang L.H., Hwa T.T. and Huang J., Formation of Novel Pattern by Programming Cell Motility, 14th Research Postgraduate Symposium, December 2 & 3, 2009, The University of Hong Kong. 2009. |
| Researcher : Jiang H |
| List of Research Outputs |
| Jiang H., Li J.X. and Wang Z.D., Vortex states in iron-based superconductors with collinear antiferromagnetic cores, Physical Review B. New York, The American Physical Society, 2009, 80: 134505: 1-8. |
| Researcher : Jiang Z |
| List of Research Outputs |
| Jiang Z., Shen S.Q. and Zhang F.C., Disorder effect of resonant spin Hall effect in a tilted magnetic field, Physical Review B. New York, The American Physical Society, 2009, 80: 195301: 1-6. |
| Jiang Z., Chu R. and Shen S.Q., Electric-field modulation of the number of helical edge states in thin-film semiconductors, Physical Review B. New York, The American Physical Society, 2010, 81: 115322: 1-4. |
| Researcher : Kong S |
| List of Research Outputs |
| Kong S., Wong Y.L., Huang Y.F. and Cheng K.S., Variation of microphysics in wind bubbles: An alternative mechanism for explaining the rebrightenings in Gamma-ray burst afterglows, Monthly Notices of the Royal Astronomical Society. United Kingdom, Royal Astronomical Society, 2010, 402: 409-416. |
| Researcher : Koning NA |
| List of Research Outputs |
| Kwok S., Chong S.N., Hsia C., Zhang Y. and Koning N.A., Discovery of a Multipolar Structure with an Equatorial Disk in NGC 6072, The Astrophysical Journal. 2010, 708: 93-100. |
| Researcher : Kovacs Z |
| List of Research Outputs |
| Harko T.C., Kovacs Z. and Lobo F.S.N., Testing Horava-Lifshitz gravity using thin accretion disk properties, Physical Review D. New York, The American Physical Society, 2009, 80: 044021: 1-7. |
| Kovacs Z., Cheng K.S. and Harko T.C., Can stellar mass black holes be quark stars ?, Monthly Notices of the Royal Astronomical Society. United Kingdom, Royal Astronomical Society, 2009, 400: 1632-1642. |
| Kovacs Z., Cheng K.S. and Harko T.C., Electron-positron energy deposition rate from neutrino pair annihilation in the equatorial plane of rapidly rotating neutron and quark stars, Monthly Notices of the Royal Astronomical Society. United Kingdom, Royal Astronomical Society, 2010, 402: 1714-1728. |
| Researcher : Kwok S |
| Project Title: | 36th COSPAR Scientific Assembly Synthesis of Organic Compounds in the Circumstellar Envelopes of Evolved Stars Prebiotic Molecules in the Circumstellar Environment |
| Investigator(s): | Kwok S |
| Department: | Science Faculty |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 07/2006 |
| Abstract: |
| N/A |
| Project Title: | The Morphological and Chemical Structure of Planetary Nebulae |
| Investigator(s): | Kwok S |
| Department: | Science Faculty |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2007 |
| Abstract: |
| To discover and study the morphological structures of PNe using high-angular resolution optical and near-infrared imaging observations, and to understand the dynamical origin of these sturctures; to map the chemical distribution of ionized gases, molecules, and solid particles in PNe in order to understand the formation history and inter-relationships between these components; to derive the kinematic structures of PNe by mapping the distribution of molecular emissions using high angular resolution imaging spectroscopy with the Submillimeter Array. |
| Project Title: | The synthesis of organic and inorganic compounds in the late stages of stellar evolution |
| Investigator(s): | Kwok S |
| Department: | Science Faculty |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2008 |
| Abstract: |
| 1) perform spectroscopic studies Asymptotic Giant Branch stars, proto-planetary nebulae, and planetary nebulae to search for new vibrational features and measure the relative strengths of the features as a function of stellar evolution; 2) perform imaging spectroscopy to determine the spatial distribution of the emitting substances in the envelopes; 3) compare with laboratory spectroscopic studies with the goal of identifying the chemical composition of unidentified emission featurres |
| Project Title: | Earth as a habitable planet |
| Investigator(s): | Kwok S |
| Department: | Science Faculty |
| Source(s) of Funding: | Seed Funding for Strategic Research Theme |
| Start Date: | 05/2009 |
| Completion Date: | 09/2012 |
| Abstract: |
| n/a |
| Project Title: | Study of Infrared Nebulae found in the Spitzer Space Telescope Galactic Plane Survey |
| Investigator(s): | Kwok S |
| Department: | Science Faculty |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2009 |
| Abstract: |
| 1) Through processing of data obtained in the GLIMPSE survey, we plan to discover and identify new infrared extended emission sources and classify them by their astronomical nature. 2) From follow-up ground-based observations in radio continuum, molecular line spectroscopy, and near-infrared imaging, we plan to study the radiative and chemical interactions between the atomic, molecular and solid-state components. 3) From the photometric colors of the nebulae, we plan to study the extent of aromatic compounds' contribution to the infrared emission of the nebulae and the abundance of organic matter in the diffuse interstellar medium. |
| Project Title: | IAU XXVII General Assembly The impact of IR and sub-mm spectroscopy on the study of stellar evolution |
| Investigator(s): | Kwok S |
| Department: | Science Faculty |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 08/2009 |
| Completion Date: | 08/2009 |
| Abstract: |
| N/A |
| List of Research Outputs |
| Deguchi S., Nakashima J., Zhang Y., Chong S.N., Koike K. and Kwok S., SiO and H2O maser observations of red supergiants in star clusters embedded in the galactic disk, Publications of the Astronomical Society of Japan. Astronomical Society of Japan, 2010, 62: 391-407. |
| Imai H., Yung H.K.B., Nakashima J., Deguchi S., Diamond P.J. and Kwok S., High Velocity Precessing Jets from the Water Fountain IRAS 18286−0959 Revealed by VLBA Observations, East Asia VLBI Workshop 2010. . |
| Irvine W., Ehrenfreund P., Boss A., Kwok S., Levasseur-Regourd A.C., Morrison D. and Udry S., Commission 51: Bioastronomy, IAU Transactions T27B. 2010, 6: 180-181. |
| Kwok S., Delivery of Complex Organic Compounds from Planetary Nebulae to the Solar System, International Journal of Astrobiology. 2009, 8: 161-167. |
| Kwok S., Chong S.N., Hsia C., Zhang Y. and Koning N.A., Discovery of a Multipolar Structure with an Equatorial Disk in NGC 6072, The Astrophysical Journal. 2010, 708: 93-100. |
| Kwok S., Infrared Imaging and Spectroscopy for the Study of the Late States of Stellar Evolution, Scientific Opportunities For new Instrumentation, Asilomar 2010. 2010. |
| Kwok S., Morphological Structures of Planetary Nebulae, Asymmetric Planetary Nebulae V. 2010. |
| Kwok S., Morphological Structures of Planetary Nebulae, Publications of the Astronomical Society of Australia. 2010, 27: 174-179. |
| Kwok S., Planetary nebulae: their evolution and role in the universe, Annual Meeting of Chinese Astronomical Society, Kaifeng, China. 中國天文學會2009年學術聯會, 2009. |
| Kwok S., The Morphology and 3-D Structures of the Ionized, Molecular, and Dust Components of Planetary Nebulae, In: Romano L.M. Corradi, Arturo Manchado and Noam Soker, Asymmetrical Planetary Nebulae IV. I.A.C. electronic publication, 2009, 11-18. |
| Kwok S., The Synthesis of Organic Compounds in the Late Stages of Stellar Evolution, Invited Colloquium at Indian Institute of Astrophysics. 2009. |
| Kwok S., The impact of IR and sub-mm spectroscopy on the study of stellar evolution, IAU XXVII General Assembly. 2009. |
| Millar T., Chu Y.H., Dyson J., Breitschwerdt D., Burton M., Cabrit S., Caselli P., de Gouveia Dal Pino E., Ferland G., Juvela M., Koo B.C., Kwok S., Lizano S., Rozyczka M., Tóth V., Tsuboi M. and Yang J., Division Vi: Interstellar Matter, IAU Transactions T27B. 2010, 6: 213-214. |
| Nakashima J., Deguchi S., Imai H., Kwok S., Koning N., Yung H.K.B., Zhang Y. and Chong S.N., Telescope Time of CARMA (Project Title: CO Mapping of the Water Fountain Object IRAS 18286-0959) , Combined Array for Research in Millimeter-wave Astronomy (CARMA). 2010. |
| Nakashima J., Kwok S., Zhang Y., Hsia C., Chong S.N., Yung B.H.K., Koning N. and Deguchi S., Telescope Time of the NRO 45m Telescope (Project Title: 3D Structure of the Helix: Verification of the Bicone Model), Nobeyama Radio Observatory, National Astronomical Observatory of Japan. 2010. |
| Sandford S., Allamandola L., Bicay M., Bregman J., Cohen M., Cruikshank D., Ennico K., Hanel R., Kwok S., Lord S., Madden S., McKelvey M., Lee T., Purcell B., Roellig T., Swain M., Tielens X., Werner M. and Willacy K., Understanding the Evolution of Molecules in Space: Implications for Astrophysics, Astrochemistry, and Astrobiology, Astro2010: The Astronomy and Astrophysics Decadal Survey, Science White Papers, no. 257. 2009, 8 pp. |
| Steffen W., López J.A., Koning N., Kwok S., Riesgo H., Richer M.G. and Morisset C., The 3D structure of the Ring Nebula , In: Romano L.M. Corradi, Arturo Manchado and Noam Soker, Asymmetrical Planetary Nebulae IV. I.A.C. electronic publication, 2009, 265-269. |
| Zhang Y. and Kwok S., Planetary Nebulae Detected in the Spitzer Space Telescope Glimpse II Legacy Survey, The Astrophysical Journal. The American Astronomical Society, 2009, 706: 252. |
| Zhang Y., Nakashima J., Kwok S., Chong S.N. and Deguchi S., Telescope Time of the NRO 45m Telescope (Project Title: A Spectral Line Survey in the 7mm Window toward the Highly Evolved Carbon Star CIT 6), Nobeyama Radio Observatory, National Astronomical Observatory of Japan. 2010. |
| Researcher : Leung JKC |
| Project Title: | Hong Kong radon map |
| Investigator(s): | Leung JKC, Jiao JJJ |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 01/2007 |
| Completion Date: | 12/2009 |
| Abstract: |
| (1) The project is related to environmental radioactivity and it has the following objectives: - To produce a Hong Kong Radon Map (GIS) in the scale of approximately 1:100,000. - To evaluate and improve the 10-point system that correlates the Radon Map with outdoor radon concentration in the environment of Hong Kong. (2) Key issues and problems: - Radon and its progenies have been known to contribute on average about 50% of the natural radiation dose to the world population. In Hong Kong, the Principal Investigators (PI) have worked on the health hazard of radon for more than a decade and have shown that the average radiation dose due to radon received by people in Hong Kong is much higher than the world average and that the average gamma radiation dose is even the highest in the world, all are results of the high U-238 and Th-232 contents in local rocks. (3) Though many workers have measured radon in Hong Kong, there is not yet a complete map of the territory showing the soil radon potential, which is based on geological, topographical and structural elements. - The radon map will show the distribution of the soil radon potential or local radon risk to the public rather than just showing the ambient radon levels at the time of measurement. (4) The maps will provide valuable information of the local radon and radionuclide situation and will be useful databases for urban planning and building construction in terms of radiation protection to the workers as well as to the general public. - The maps will only cover the rural areas but not the built-up areas. - These kinds of work are practiced in western countries only in recent years. (5) A 10-point system was invented recently by the German co-investigator to correlate indoor radon concentration and soil radon potential with great success. - Because Hong Kong has a lot of coastal areas where the radon potential could be affected by the sea in addition to land topography, the 10-point system has to be modified and adapted to the environment of Hong Kong. (6) Deliverables - A GIS Hong Kong Radon Map in the scale of approximately 1:100,000. - A GIS map of distribution of soil radon concentrations, soil gas permeability and soil radionuclide contents. - A modified 10-point system for the environment of Hong Kong. (7) To establish the relation of indoor radon concentration in low-rises and lower floors of buildings with the radon potential. |
| Project Title: | Development of High Energy Particle Physics |
| Investigator(s): | Leung JKC, Cheng KS, Pun JCS |
| Department: | Physics |
| Source(s) of Funding: | University Development Fund - General Award |
| Start Date: | 07/2007 |
| Abstract: |
| To build up the modern instrumentation and data acquisition system for high energy particle physics; and to train research students and prepare them to be able to participate in the Daya Bay Experiment. |
| Project Title: | Muon-induced neutron production in the Aberdeen Tunnel underground laboratory |
| Investigator(s): | Leung JKC, Pun JCS |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 01/2008 |
| Abstract: |
| To participate in a major international particle physics experiment that is being constructed right in our neighborhood. To design and build a neutron detector comprising of Gd-doped liquid scintillator (Gd-LS) and completed with a muon tracker. To study the production of neutrons in the neutron detector by the incident cosmic muons. To study the other background radiation effects such as gammas and radon from rocks. To characterize the Gd-LS in terms of its radiation response, light yield and attenuation, long-term stability, etc and also to test its compatibility with various types of construction materials. To develop a calibration system based on LEDs and diffuser balls for calibrating the efficiency of the neutron detector. |
| List of Research Outputs |
| Ablikim M., Achasov M.N., An L., An Q., An Z.H., Bai J.Z., Ban Y., Berger N., Bian J.M., Boyko I., Briere R.A., Bytev V., Cai X., Cao G.F., Cao X.X., Chang J.F., Chelkov G., Chen G., Chen H.S., Chen J.C., Chen L.P., Chen M.L., Chen P., Chen S.J., Chen Y.B., Chu Y.P., Cronin-Hennessy D., Dai H.L., Dai J.P., Dedovich D., Deng Z.Y., Denysenko I., Destefanis M., Ding Y., Dong L.Y., Dong M.Y., Du S.X., Duan M.Y., Fang J., Feng C.Q., Fu C.D., Fu J.L., Gao Y., Geng C., Goetzen K., Gong W.X., Greco M., Grishin S., Gu Y.T., Guo A.Q., Guo L.B., Guo Y.P., Han S.Q., Harris F.A., He K.L., He M., He Z.Y., Heng Y.K., Hou Z.L., Hu H.M., Hu J.F., Hu T., Hu X.W., Huang B., Huang G.M., Huang J.S., Huang X.T., Huang Y.P., Ji C.S., Ji Q., Ji X.B., Ji X.L., Jia L.K., Jiang L.L., Jiang X.S., Jiao J.B., Jin D.P., Jin S., Komamiya S., Kuehn W., Lange S., Leung J.K.C., Li C., Li C., Li D.M., Li F., Li G., Li H.B., Li J., Li J.C., Li L., Li L., Li Q.J., Li W.D., Li W.G., Li X.L., Li X.N., Li X.Q., Li X.R., Li Y.X., Li Z.B., Liang H., Liang T.R., Liang Y.T., Liang Y.F., Liao G.R., Liao X.T., Liu B., Liu C.L., Liu C.X., Liu C.Y., Liu F.H., Liu F., Liu F., Liu G.C., Liu H., Liu H.B., Liu H.M., Liu H.W., Liu J., Liu J.P., Liu K., Liu K.Y., Liu Q., Liu S.B., Liu X.H., Liu Y.B., Liu Y.F., Liu Y.W., Liu Y., Liu Z.A., Lu G.R., Lu J.G., Lu Q.W., Lu X.R., Lu Y.P., Luo C.L., Luo M.X., Luo T., Luo X.L., Ma C.L., Ma F.C., Ma H.L., Ma Q.M., Ma X., Ma X.Y., Maggiora M., Mao Y.J., Mao Z.P., Min J., Mo X.H., Muchnoi N.Y., Nefedov Y., Ning F.P., Olsen S.L., Ouyang Q., Pelizaeus M., Peters K., Ping J.L., Ping R.G., Poling R., Pun J.C.S., Qi M., Qian S., Qiao C.F., Qiu J.F., Rong G., Ruan X.D., Sarantsev A., Shao M., Shen C.P., Shen X.Y., Sheng H.Y., Sonoda S., Spataro S., Spruck B., Sun D.H., Sun G.X., Sun J.F., Sun S.S., Sun X.D., Sun Y.J., Sun Y.Z., Sun Z.J., Sun Z.T., Tang C.J., Tang X., Tang X.F., Tian H.L., Toth D., Varner G.S., Wan X., Wang B.Q., Wang J.K., Wang K., Wang L.L., Wang L.S., Wang P., Wang P.L., Wang Q., Wang S.G., Wang X.D., Wang X.L., Wang Y.D., Wang Y.F., Wang Y.Q., Wang Z., Wang Z.G., Wang Z.Y., Wei D.H., Wen S.P., Wiedner U., Wu L.H., Wu N., Wu W., Wu Y.M., Wu Z., Xiao Z.J., Xie Y.G., Xu G.F., Xu G.M., Xu H., Xu M., Xu M., Xu X.P., Xu Y., Xu Z.Z., Xue Z., Yan L., Yan W.B., Yan Y.H., Yang H.X., Yang M., Yang P., Yang S.M., Yang Y.X., Ye M., Ye M.H., Yu B.X., Yu C.X., Yu L., Yuan C.Z., Yuan Y., Zeng Y., Zhang B.X., Zhang B.Y., Zhang C.C., Zhang D.H., Zhang H.H., Zhang H.Y., Zhang J.W., Zhang J.Y., Zhang J.Z., Zhang L., Zhang S.H., Zhang X.Y., Zhang Y., Zhang Y.H., Zhang Z.P., Zhao C., Zhao H.S., Zhao J.W., Zhao J.W., Zhao L., Zhao L., Zhao M.G., Zhao Q., Zhao S.J., Zhao T.C., Zhao X.H., Zhao Y.B., Zhao Z.G., Zhemchugov A., Zheng B., Zheng J.P., Zheng Y.H., Zheng Z.P., Zhong B., Zhong J., Zhou L., Zhou Z.L., Zhu C., Zhu K., Zhu K.J., Zhu Q.M., Zhu X.W., Zhu Y.S., Zhu Z.A., Zhuang J., Zou B.S., Zou J.H., Zuo J.X. and Zweber P., Branching fraction measurements of chi(c0) and chi(c2) to pi(0)pi(0) and eta eta, Physical Review D. New York, The American Physical Society, 2010, 81: 052005: 1-8. |
| Ablikim M., Achasov M.N., An L., An Q., An Z.H., Bai J.Z., Ban Y., Berger N., Bian J.M., Boyko I., Briere R.A., Bytev V., Cai X., Cao G.F., Cao X.X., Chang J.F., Chelkov G., Chen G., Chen H.S., Chen J.C., Chen L.P., Chen M.L., Chen P., Chen S.J., Chen Y.B., Chu Y.P., Cronin-Hennessy D., Dai H.L., Dai J.P., Dedovich D., Deng Z.Y., Denysenko I., Destefanis M., Ding Y., Dong L.Y., Dong M.Y., Du S.X., Duan M.Y., Fang J., Feng C.Q., Fu C.D., Fu J.L., Gao Y., Geng C., Goetzen K., Gong W.X., Greco M., Grishin S., Gu Y.T., Guo A.Q., Guo L.B., Guo Y.P., Han S.Q., Harris F.A., He K.L., He M., He Z.Y., Heng Y.K., Hou Z.L., Hu H.M., Hu J.F., Hu T., Hu X.W., Huang B., Huang G.M., Huang J.S., Huang X.T., Huang Y.P., Ji C.S., Ji Q., Ji X.B., Ji X.L., Jia L.K., Jiang L.L., Jiang X.S., Jiao J.B., Jin D.P., Jin S., Komamiya S., Kuehn W., Lange S., Leung J.K.C., Li C., Li C., Li D.M., Li F., Li G., Li H.B., Li J., Li J.C., Li L., Li L., Li Q.J., Li W.D., Li W.G., Li X.L., Li X.N., Li X.Q., Li X.R., Li Y.X., Li Z.B., Liang H., Liang T.R., Liang Y.T., Liang Y.F., Liao G.R., Liao X.T., Liu B., Liu C.L., Liu C.X., Liu C.Y., Liu F.H., Liu F., Liu F., Liu G.C., Liu H., Liu H.B., Liu H.M., Liu H.W., Liu J., Liu J.P., Liu K., Liu K.Y., Liu Q., Liu S.B., Liu X.H., Liu Y.B., Liu Y.F., Liu Y.W., Liu Y., Liu Z.A., Lu G.R., Lu J.G., Lu Q.W., Lu X.R., Lu Y.P., Luo C.L., Luo M.X., Luo T., Luo X.L., Ma C.L., Ma F.C., Ma H.L., Ma Q.M., Ma X., Ma X.Y., Maggiora M., Mao Y.J., Mao Z.P., Min J., Mo X.H., Muchnoi N.Y., Nefedov Y., Ning F.P., Olsen S.L., Ouyang Q., Pelizaeus M., Peters K., Ping J.L., Ping R.G., Poling R., Pun J.C.S., Qi M., Qian S., Qiao C.F., Qiu J.F., Rong G., Ruan X.D., Sarantsev A., Shao M., Shen C.P., Shen X.Y., Sheng H.Y., Sonoda S., Spataro S., Spruck B., Sun D.H., Sun G.X., Sun J.F., Sun S.S., Sun X.D., Sun Y.J., Sun Y.Z., Sun Z.J., Sun Z.T., Tang C.J., Tang X., Tang X.F., Tian H.L., Toth D., Varner G.S., Wan X., Wang B.Q., Wang J.K., Wang K., Wang L.L., Wang L.S., Wang P., Wang P.L., Wang Q., Wang S.G., Wang X.D., Wang X.L., Wang Y.D., Wang Y.F., Wang Y.Q., Wang Z., Wang Z.G., Wang Z.Y., Wei D.H., Wen S.P., Wiedner U., Wu L.H., Wu N., Wu W., Wu Y.M., Wu Z., Xiao Z.J., Xie Y.G., Xu G.F., Xu G.M., Xu H., Xu M., Xu M., Xu X.P., Xu Y., Xu Z.Z., Xue Z., Yan L., Yan W.B., Yan Y.H., Yang H.X., Yang M., Yang P., Yang S.M., Yang Y.X., Ye M., Ye M.H., Yu B.X., Yu C.X., Yu L., Yuan C.Z., Yuan Y., Zeng Y., Zhang B.X., Zhang B.Y., Zhang C.C., Zhang D.H., Zhang H.H., Zhang H.Y., Zhang J.W., Zhang J.Y., Zhang J.Z., Zhang L., Zhang S.H., Zhang X.Y., Zhang Y., Zhang Y.H., Zhang Z.P., Zhao C., Zhao H.S., Zhao J.W., Zhao J.W., Zhao L., Zhao L., Zhao M.G., Zhao Q., Zhao S.J., Zhao T.C., Zhao X.H., Zhao Y.B., Zhao Z.G., Zhemchugov A., Zheng B., Zheng J.P., Zheng Y.H., Zheng Z.P., Zhong B., Zhong J., Zhou L., Zhou Z.L., Zhu C., Zhu K., Zhu K.J., Zhu Q.M., Zhu X.W., Zhu Y.S., Zhu Z.A., Zhuang J., Zou B.S., Zou J.H., Zuo J.X. and Zweber P., Measurements of h(c) (P-1(1)) in psi ' decays, Physical Review Letters. New York, The American Physical Society, 2010, 104: 132002: 1-6. |
| Ablikim M., Achasov M.N., An L., An Q., An Z.H., Bai J.Z., Ban Y., Berger N., Bian J.M., Boyko I., Briere R.A., Bytev V., Cai X., Cao G.F., Cao X.X., Chang J.F., Chelkov G., Chen G., Chen H.S., Chen J.C., Chen L.P., Chen M.L., Chen P., Chen S.J., Chen Y.B., Chu Y.P., Cronin-Hennessy D., Dai H.L., Dai J.P., Dedovich D., Deng Z.Y., Denysenko I., Destefanis M., Ding Y., Dong L.Y., Dong M.Y., Du S.X., Duan M.Y., Fang J., Feng C.Q., Fu C.D., Fu J.L., Gao Y., Geng C., Goetzen K., Gong W.X., Greco M., Grishin S., Gu Y.T., Guo A.Q., Guo L.B., Guo Y.P., Han S.Q., Harris F.A., He K.L., He M., He Z.Y., Heng Y.K., Hou Z.L., Hu H.M., Hu J.F., Hu T., Hu X.W., Huang B., Huang G.M., Huang J.S., Huang X.T., Huang Y.P., Ji C.S., Ji Q., Ji X.B., Ji X.L., Jia L.K., Jiang L.L., Jiang X.S., Jiao J.B., Jin D.P., Jin S., Komamiya S., Kuehn W., Lange S., Leung J.K.C., Li C., Li C., Li D.M., Li F., Li G., Li H.B., Li J., Li J.C., Li L., Li L., Li Q.J., Li W.D., Li W.G., Li X.L., Li X.N., Li X.Q., Li X.R., Li Y.X., Li Z.B., Liang H., Liang T.R., Liang Y.T., Liang Y.F., Liao G.R., Liao X.T., Liu B., Liu C.L., Liu C.X., Liu C.Y., Liu F.H., Liu F., Liu F., Liu G.C., Liu H., Liu H.B., Liu H.M., Liu H.W., Liu J., Liu J.P., Liu K., Liu K.Y., Liu Q., Liu S.B., Liu X.H., Liu Y.B., Liu Y.F., Liu Y.W., Liu Y., Liu Z.A., Lu G.R., Lu J.G., Lu Q.W., Lu X.R., Lu Y.P., Luo C.L., Luo M.X., Luo T., Luo X.L., Ma C.L., Ma F.C., Ma H.L., Ma Q.M., Ma X., Ma X.Y., Maggiora M., Mao Y.J., Mao Z.P., Min J., Mo X.H., Muchnoi N.Y., Nefedov Y., Ning F.P., Olsen S.L., Ouyang Q., Pelizacus M., Peters K., Ping J.L., Ping R.G., Poling R., Pun J.C.S., Qi M., Qian S., Qiao C.F., Qiu J.F., Rong G., Ruan X.D., Sarantsev A., Shao M., Shen C.P., Shen X.Y., Sheng H.Y., Sonoda S., Spataro S., Spruck B., Sun D.H., Sun G.X., Sun J.F., Sun S.S., Sun X.D., Sun Y.J., Sun Y.Z., Sun Z.J., Sun Z.T., Tang C.J., Tang X., Tang X.F., Tian H.L., Toth D., Varner G.S., Wan X., Wang B.Q., Wang J.K., Wang K., Wang L.L., Wang L.S., Wang P., Wang P.L., Wang Q., Wang S.G., Wang X.D., Wang X.L., Wang Y.D., Wang Y.F., Wang Y.Q., Wang Z., Wang Z.G., Wang Z.Y., Wei D.H., Wen S.P., Wiedner U., Wu L.H., Wu N., Wu Y.M., Wu Z., Xiao Z.J., Xie Y.G., Xu G.F., Xu G.M., Xu H., Xu M., Xu M., Xu X.P., Xu Y., Xu Z.Z., Xue Z., Yan L., Yan W.B., Yan Y.H., Yang H.X., Yang M., Yang P., Yang S.M., Yang Y.X., Ye M., Ye M.H., Yu B.X., Yu C.X., Yu L., Yuan C.Z., Yuan Y., Zeng Y., Zhang B.X., Zhang B.Y., Zhang C.C., Zhang D.H., Zhang H.H., Zhang H.Y., Zhang J.W., Zhang J.Y., Zhang J.Z., Zhang L., Zhang S.H., Zhang X.Y., Zhang Y., Zhang Y.H., Zhang Z.P., Zhao C., Zhao H.S., Zhao J.W., Zhao J.W., Zhao L., Zhao L., Zhao M.G., Zhao Q., Zhao S.J., Zhao T.C., Zhao X.H., Zhao Y.B., Zhao Z.G., Zhemchugov A., Zheng B., Zheng J.P., Zheng Y.H., Zheng Z.P., Zhong B., Zhong J., Zhou L., Zhou Z.L., Zhu C., Zhu K., Zhu K.J., Zhu Q.M., Zhu X.W., Zhu Y.S., Zhu Z.A., Zhuang J., Zou B.S., Zou J.H., Zuo J.X. and Zweber P., Observation of a p(p)over-bar mass threshold enhancement in psi ' -> pi(+)pi(-)J/psi(J/psi -> gamma p(p)over-bar) decay, Chinese Physics C . Chinese Physical Soc, 2010, 34: 421-426. |
| Zheng D.Q., Leung J.K.C. and Lee B.Y., An ensemble Kalman filter for atmospheric data assimilation: Application to wind tunnel data, Atmospheric Environment. Amsterdam, Elsevier Ltd., 2010, 44: 1699-1705. |
| Researcher : Li H |
| List of Research Outputs |
| Li H., Zhong G.H., Lin H.Q. and Xie M.H., Reactive interface formation and Co-induced (√7×√7) superstructure on a GaN(0001) pseudo-(1×1) substrate surface, Physical Review B (Brief Reports). New York, The American Physical Society, 2010, 81: 233302: 1-4. |
| Li H., He K., Xie M.H., Wang N., Jia J.F. and Xue Q.K., Surface modification for epitaxial growth of single crystalline cobalt thin films with uniaxial magnetic anisotropy on GaN(0001)-1×1 surfaces, New Journal of Physics. Bristol, IOP Publishing Limited, 2010, 12: 073007: 1-9. |
| Researcher : Li Y |
| List of Research Outputs |
| Ai Q., Li Y., Zheng H. and Sun C.P., Quantum anti-Zeno effect without rotating wave approximation, Physical Review A. New York, The American Physical Society, 2010, 81: 042116: 1-12. |
| Huang J.F., Li Y., Liao J.Q., Kuang L.M. and Sun C.P., Dynamic sensitivity of photon-dressed atomic ensemble with quantum criticality, Physical Review A. New York, The American Physical Society, 2009, 80: 063829: 1-7. |
| Li Y., Zhang P. and Wang Z.D., Extended JC-Dicke model for two-component atomic BEC inside a cavity, European Physical Journal D. Springer, 2010, 58: 379-384. |
| Wang Y.D., Li Y., Xue F., Bruder C. and Semba K., Cooling a micromechanical resonator by quantum back-action from a noisy qubit, Physical Review B. New York, The American Physical Society, 2009, 80: 144508: 1-4. |
| Researcher : Lim JJL |
| Project Title: | Assembly, Gas Content, and Star Formation History of Galaxies (Galaxies 2009) Cool Molecular Gas in Central Cluster Giant Elliptical Galaxies |
| Investigator(s): | Lim JJL |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 09/2009 |
| Completion Date: | 09/2009 |
| Abstract: |
| N/A |
| Project Title: | Excitation of and Star Formation in the Multi-Phase Nebula at the core of the Perseus Cluster |
| Investigator(s): | Lim JJL |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 06/2010 |
| Abstract: |
| Small groups to large clusters of galaxies are immersed in hot (~107–108 K) X-ray-emitting gas that constitutes the bulk of their baryonic mass. Much of this gas originated from the Cosmic Web or was stripped from dark matter haloes and then shocked to high temperatures as it flowed into the gravitational potential well of a mass concentration. In relaxed groups or clusters (i.e., those not experiencing major mergers with other groups or clusters), the hot gas is close to pressure equilibrium and therefore increases inwards in density thereby exhibiting an even steeper inward increase in X-ray intensity. About 30 years ago, Cowie & Binney (1979) and Fabian & Nulsen (1979) independently pointed out that the hot gas near the centers of such groups or clusters should cool (by virtue of its intense X-ray emission) on relatively short timescales and flow inwards, thereby resulting in an X-ray cooling flow. Subsequent studies have sown deep skepticism on the existence of X-ray cooling flows. Substantial amounts of relatively cool (<106 K) gas have been found preferentially in the central giant elliptical galaxies of clusters suspected to harbor strong X-ray cooling flows, but not at quantities anywhere near the predicted levels. Recent high-energy-resolution X-ray spectra show a decrease in gas temperature towards cluster centers (as would be expected if the gas is cooling), but fail to reveal any detectable gas at temperatures below about one-third the bulk ambient temperature (Peterson et al. 2003; Peterson & Fabian 2006). These results imply that any X-ray cooling flows must have a mass-deposition rate at least 10 times lower than previously thought. Finally, recent high-angular-resolution X-ray images show that radio jets from the central cluster galaxy strongly disturb the hot gas in the cluster core, and have more than enough energy to reheat and therefore greatly diminish if not entirely quench any X-ray cooling flow (Churazov et al. 2002; Bîrzan et al. 2004). Despite these misgivings, the presence of large amounts of relatively cool gas and evidence for recent star formation preferentially in the central galaxies of clusters suspected to harbor strong X-ray cooling flows provide circumstantial evidence that such flows do occur, albeit in a more complex manner than originally thought. The central problem now is to unravel the interplay between cooling and reheating of the X-ray gas in the cluster core, for which among the key issues are the origin, nature, and fate of the relatively cool gas. Our proposal focuses on the Perseus cluster, one of the closest and the X-ray-brightest cluster in the sky. It harbors what is suspected to be by far the strongest X-ray cooling flow of any cluster up to and significantly beyond its distance. Its central galaxy, NGC 1275, possesses all the properties – copious relatively cool gas, recent star formation – peculiar to central cluster galaxies that inhabit suspected X-ray cooling flows. The Perseus cluster is therefore the most important testbed for ideas on X-ray cooling flows, and the cluster in which the processes at work can be studied in greatest detail. The relatively cool gas in NGC 1275 is distributed in a spectacular filamentary nebula. Our (Lim, Ao, & Dinh 2008; Ho, Lim, & Dinh 2009) studies of the coolest and densest component of this nebula – molecular hydrogen gas as traced in CO – provides the most direct evidence yet that (the bulk of) this gas was accreted from the intracluster medium, and hence the strongest evidence yet for a X-ray cooling flow in this (or indeed any) cluster. We have submitted a proposal to the RGC (in early October 2009) for follow-up studies of NGC 1275 in cool molecular gas, as well as kinematic studies of the hot molecular hydrogen gas (through its near-IR vibrational lines) and ionized gas (Hα line) to determine not just their spatial but also kinematic relationship with the cool molecular gas. Recently, we started a program to measure the kinematics of the Hα gas in NGC 1275. We realized then that the instrument used allows us to strike in an entirely new direction to address two other important issues about the nebula in NGC 1275: 1.How is the nebula excited? Long a subject of intensive debate, this goes to the heart of understanding the nature of this nebula. Radiative heating (e.g., from the X-ray gas) is known to be energetically unfavorable or implausible for the bulk of the nebula. Recently, Ferland et al. (2009) presented the most sophisticated and complete model yet for the infrared to optical spectrum of the nebula in NGC 1275 based on non-radiative heating mechanisms. Their model implicates excitation predominantly if not entirely by ionizing particles over non-ionizing heating sources (e.g., MHD waves). 2.What is the fate of the nebula? One long-suspected possibility is that some of this gas forms stars. Only one (confirmed) massive star-forming region has so far been found coincident with the nebula in NGC 1275 (Shields & Filippenko 1990), but such searches cover only a tiny fraction of this nebula. A complete census of massive star-forming regions within the nebula is urgently needed. |
| List of Research Outputs |
| Ngoc P.B., Lim J.J.L., Donati J.F., Johns-Krull C.M. and Martin E.L., Magnetic field topology in low-mass stars: Spectropolarimetric observations of M dwarfs, The Astrophysical Journal. The American Astronomical Society, 2009, 704: 1721-1729. |
| Researcher : Ling FCC |
| Project Title: | Ion implantation of zinc oxide material: dopant activation and defect characterization |
| Investigator(s): | Ling FCC |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 01/2007 |
| Abstract: |
| (1) Most of the attempts to introduce doping into ZnO were done on deposition grown materials (i.e. MBE, CVD or PVD etc.). However, ion implantation doping technique of ZnO is still immature and required more attention. With the aim to introduce n-type and p-type doping, ion implantation in ZnO materials is proposed to be performed. (2) Al and/or Ga implantations are proposed to introduce the n-type doping into the material. For p-type doping, N ion will be the focus of studies. Co-doping with group III and V elements will also be attempted to achieve the p-type doping. Studies of activating the implanted dopants by annealing will be performed. (3) The deep level defects induced by the ion implantation process will be studied by deep level transient spectroscopy. Attention will also be paid to the annealing effect of these deep level defects. Temperature dependent Hall measurement will also be performed to investigate the shallow acceptor/donor states introduced. (4) Positron annihilation spectroscopic technique will be employed to study the open volume defects created by the ion implantation process. |
| Project Title: | Defect study of hydrothermally grown zinc oxide single crystal |
| Investigator(s): | Ling FCC |
| Department: | Physics |
| Source(s) of Funding: | Small Project Funding |
| Start Date: | 12/2007 |
| Completion Date: | 11/2009 |
| Abstract: |
| Since the invention of the p-n junction diode which was the most fundamental structure of semiconductor devices, control and use of defects are the essential entity in semiconductor materials and devices fabrications. With proper doping which involved the introduction of impurity defect into the semiconductor at a tiny level of one impurity atom per $10^{3}$ to $10^{10}$ host atoms (that corresponds to the dopant concentration of $10^{20}$ to $10^{13} cm^{-3}$), the carrier concentration as well as the type of the majority free carrier can be controlled [1]. It is because the doping impurity presents a shallow donor/acceptor level in the band gap (having ionization energy of several tens of meV), and the ionization of the donor/acceptor would generate free carriers at the conduction/valance band. Other than the impurity defect, intrinsic defects (like vacancy, antisite and etc) would also influence the electrical property of the material. One of such example is that undoped gallium antimonide is always p-type having a hole concentration of about $10^{16} cm^{-3}$ and this p-type nature is due to the intrinsic antisite shallow acceptor defect GaSb (reference [2] and references therein). Deep level defects in semiconductors have the effects of compensating the free carriers and decreasing the free carrier lifetime. One of the applications of defect engineering using the deep level defects is the case of semi-insulting GaAs, for which the intrinsic defect EL2 (at ~EC-0.82eV) is the compensating deep level defect [3]. As defects play important role to determine the electrical and the optical properties of the semiconductor materials, understanding the defects is crucial for the successful material and device fabrications. Despite of great deal of effort having been devoted to understand the defects in ZnO, knowledge of defects in ZnO is far from complete [4,5]. Zinc oxide single crystal can now be grown by different methods, namely the methods of vapor phase (VP), melt (MLT) and hydrothermal (HYD). The undoped single crystals grown by the methods of VP and MLT are usually of n-type and have the carrier concentration of $10^{15}-10^{16}cm^{-3}$. This is due to the ionization of the residual shallow donor located at EC-30meV. However, the identity of the residual donor is still controversial and has been associated with Zn interstitial, O vacancy and H impurity. P-type doping of ZnO and fabrication of good quality Schottky contact remained the two important issues for developing ZnO-based device technology. The difficulty of solving these two problems deeply lies in the insufficient understanding of the defects in the ZnO material. For the case of HYD grown ZnO single crystal, the material is usually of high resistance, having a resistivity of $~10^{3}\ohmcm$. It was suggested that the high concentration of Li acceptor in the HYD grown ZnO compensated the material and thus the material’s electrical property was determined by the existing deep level donors. Deep level transient spectroscopy (DLTS) is the best method for studying the deep levels in semiconductors. DLTS can reveal the concentration, the position of the energy state and the capture cross section of the deep level defects. However, DLTS measurement required the fabrication of a rectifying junction, like a p-n junction or a Schottky diode, and this is rather a extremely difficult task for material having high resistance. This leads to the present situation that there have been very few studies devoted to investigate the defects in HYD grown ZnO. In the present proposal, we suggest to investigate the defects in HYD grown ZnO while bearing the following objectives: (1) Characterize and identify the vacancy type defects in HYD grown ZnO by positron annihilation spectroscopy (PAS); (2) Characterize and identify the electrical and optical active defects in HYD grown ZnO by the methods of thermally stimulated current (TSC); and (3) Understand how the defects in the HYD grown ZnO determine the electrical property of the material. REFERENCES: [1] H. J. Queisser and E. E. Haller, Science, vol.281, 945 (1998). [2] C. C. Ling, M. K. Lui, S. K. Ma, X. D. Chen, S. Fung and C. D. Beling, Appl. Phys. Lett. Vol.85, 384 (2004). [3] G. M. Martin and S. Makram-Ebeid, in Deep Centers in Semiconductors, A State-of-the-Art Approach, ed. S. T. Pantelides, 2nd Ed., Gordon and Breach Science Publishers, 1992, page 457. [4] ‘Zinc oxide bulk, thin films and nanostructure, processing, properties and applications’, eds. C. Jagadish and S. J. Pearton, Elsevier (2006). [5] Ü. Özgür et al, J. Appl. Phys. 98, 041301 (2005). [6] Z. Q. Fang, B. Claflin and D. C. Look, J. Appl. Phys. Vol.101, 086106 (2007). [7] K. Maeda, M. Sato, I. Niikura and T. Fukuda, Semicond. Sci. Technol. Vol.20, S49 (2005). |
| Project Title: | Ion-implantation of ZnO material: dopant activation and defect characterization |
| Investigator(s): | Ling FCC, Djurisic A, Gu Q |
| Department: | Physics |
| Source(s) of Funding: | Germany/Hong Kong Joint Research Scheme |
| Start Date: | 01/2008 |
| Completion Date: | 12/2009 |
| Abstract: |
| 1. Most of the previous attempts on p-type doping of ZnO were carried out by deposition method (for example, MBE, CVD, PVD and etc.) using the dopant nitrogen. However, ion implantation is an alternative for introducing selective region doping into semiconductor materials. With the aim to introduce p-tupe doping in n-ZnO material, group V doping and groups III-V co-doping by ion implantation will be carried out on n-type ZnO single crystal and vertical nanorod array. 2. Ion implantation induced defects will be studied by Hall measurement, deep level transient spectroscopy, photoluminescence and positron annihilation spectroscopy to understand how these defects determine the electrical and the optical properties. Thermal evolution of these defects and the subsequent change in electrical and optical properties will also be investigated by the annealing study. |
| Project Title: | P-type doping of ZnO materials: influence of compensation by deep donors and acceptors |
| Investigator(s): | Ling FCC |
| Department: | Physics |
| Source(s) of Funding: | Small Project Funding |
| Start Date: | 11/2008 |
| Abstract: |
| Reliable techniques of n-type and p-type doping are essential for successful semiconductor device fabrication. Doping is usually achieved by introducing the appropriate impurities which act as shallow donor or acceptor having ionization energies much less than the thermal energy of room temperature. However, the efficiency of doping is influenced by other factors, for example: (1) the introduced impurity may not sit at the correct site that would form the desired shallow acceptor or donor states; and (2) the presence of deep level state that would compensate the doped material. This thus implies successful semiconductor doping lays on the foundation of defect characterization and control [1]. Unintentionally doped zinc oxide is n-type with electron concentration varying from ~10^{16}cm^{-3} to semi-insulating depending on the growing technique. Although this fact has been well known for a long time, the origin for the nominal n-type conductivity was still controversial. It has been attributed to hydrogen impurity and intrinsic defect [2-5]. Heavily n-type impurity doping of ZnO with carrier concentration up to 10^{20}cm^{-3} has be achieved by Group III elements like Ga and Al (for example reference [6]). In contrast to n-type doping, p-type doping for ZnO is difficult [7,8]. First principal calculations showed that Group V atoms sitting at the O-site of ZnO were acceptors, while ionization energies of their shallowest acceptor states increased with the atomic number. N_{O} is a shallow acceptor, while P, As and Sb occupying the O-site are deep acceptors [9]. Based on these results nitrogen has received most extensive studies as p-type dopant in ZnO, although experimental findings showed that it was difficult and non-reproducible. Despite of some success of doping ZnO with nitrogen (reference [10] and Chapter 2 in reference [8]), for many cases introducing nitrogen into ZnO yielded high resistance material rather than p-type materials. This has been suggested to be associated with: (1) the strong bond between the nitrogen atoms while N2 was used as the doping agent; and (2) the introduction of deep level defects that acted as compensation centers. Arsenide doping of ZnO has recently been under the focus as there were reports on successful fabrication of p-type ZnO by As-doping, although the p-type formation mechanism was not thoroughly understood and controversial [11-12]. In our recent studies, we have studied fabricating p-type ZnO materials with N-doping, As-doping and nominal undoped condition [13-16], Within some particular growing conditions, p-type doping of ZnO has been acheived. With the aim to understand the influence of the deep level defects on the efficiency of p-type doping of ZnO, we have the following objectives in the present proposal. (1) Systematically study the efficiency of ZnO p-type doping by arsenide and nitrogen, under different growing conditions. (2) Study the deep level defects of these ZnO samples grown under different conditions using the deep level transient spectroscopy (DLTS), thermally stimulated current (TSC) spectroscopy, and photoluminescence (PL). The correlation between the p-type doping efficiency and the results of the deep level defect study will then be carefully studied. REFERENCE: [1] H. J. Queisser and E. E. Haller, Science vol.281, 945 (1998). [2] C. G. Van de Walle, Phys. Rev. Lett. Vol.85, 1012 (2000). [3] A. Janotti and C. G. Van de Walle, Nature Materials vol.6, 44 (2007). [4] D. C. Look et al, Phys. Rev. Lett. Vol.82, 2552 (1999). [5] D. C. Look et al, Phys. Rev. Lett. Vol.95, 225502 (2005). [6] H. J. Ko et al, Appl. Phys. Lett. Vol. 77, 3761 (2000). [7] Ü. Özgür et al, J. Appl. Phys. 98, 041301 (2005). [8] C. Jagadish and S. J. Pearton, ed. Zinc oxide bulk, thin films and nanostructures, processing, properties and applications (Elsevier, 2006). [9] C. H. Park et al, Phys. Rev. B vol.66, 073202 (2002). [10] A. Tsukazaki et al, Nature Materials, vol.4, 42 (2005). [11] U. Wahl et al, Phys. Rev. Lett. Vol.95, 215503 (2005). [12] S. Limpijumnong et al, Appl. Phys. Lett. Vol. 89, 222113 (2006). [13] X. D. Chen et al, Appl. Phys. Lett. vol.88, 132104 (2006). [14] Y.F. Hsu, Adv. Funct. Mater. Vol.18, 1020 (2008). [15] Q. L. Gu et al, Appl. Phys. Lett. vol. 92, 222109 (2008). [16] C. Y. Zhu et al, European Materials Research Society 2008 Spring Meeting, Strasbourg, France, May 26-30, 2008. |
| Project Title: | Defect study of ZnO materials |
| Investigator(s): | Ling FCC, Djurisic A |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 12/2008 |
| Abstract: |
| 1) To investigate the vacancy type defects with PAS and first principle calculation in order to unambiguously determine the characteristic features (for example characteristic positron lifetime and electronic momentum distribution) of different positron annihilation states (lattice state and vacancy states) in ZnO, and to reveal the microstructures of the vacancy type defects as identified in the ZnO materials. Annealing behaviors of these vacancy type defects will also be studied. 2) To investigate the shallow acceptor and the compensation of the p-type ZnO materials with the focus placing on the vertical undoped p-type nanorod array, with the use of the TDH measurement, DLTS and/or TSCS. 3) To carry out Mn and Co ion implantation into ZnO and to investigate the correlation between the shallow donor and the magnetic property of the system. |
| Project Title: | Intrinsic deep level defects in zinc oxide materials studied by deep level transient spectroscopy |
| Investigator(s): | Ling FCC |
| Department: | Physics |
| Source(s) of Funding: | Small Project Funding |
| Start Date: | 01/2010 |
| Abstract: |
| Although ZnO is a wide band gap semiconductor that has recently attracted intense attention, understanding of its intrinsic defects is still limited and controversial. Undoped ZnO material is n-type conduction. The origin of the n-type conductivity is still under debate, and is associated to H-impurity and intrinsic defect [1,2]. The origin of the green luminescence found in ZnO was still uncertain, and has been attributed to Cu impurity, Zn-vacancy, O-vacancy and O-antisite [1,2]. Electron paramagnetic resonance (EPR) has been used to obtain a relatively concrete identification and the corresponding g values of O-vacancy and Zn-vacancy in ZnO (Table IV in reference [3]). However there is no concrete experimental assignment on the transition energy levels in the ZnO bandgap. There were some theoretical studies carried out to study the intrinsic defects in ZnO. Janotti and Van de Walle [3] have studied the native point defects in ZnO using the first principal calculation. It was found that oxygen vacancy, zinc vacancy and oxygen antisite would have transition energy states in the band gap. Oxygen vacancy is an U-negative deep donor having the energy level at E(2+/0)~1eV. Zn vacancy is a deep acceptors having the transition levels at E(0/-)=0.18eV and E(-/2-)=0.87eV. Oxygen antisite has two acceptor states in the band gap, namely and E(0/-)=1.52eVand E(-/2-)=1.77eV. Deep level defects in semiconductors are usually studied by photoluminescence (PL) and DLTS. However, the origins of the different PL defect emissions that commonly observed in ZnO materials are relatively not certain and controversial [1,2]. For intrinsic defects in ZnO investigated by DLTS, studies were even rarely carried out and no microstructure identification of DLTS signal was well established. The poor understanding of deep level traps also limits the development of ZnO device technology in other aspects. For example, ion-implantation is a useful technology for introducing selective area n-type and p-type doping in semiconductor device technology. However non-desirable deep traps acting as compensating centers would also be created by the ion-implantation. DLTS is a very useful tool to investigate these deep traps while developing device technology in other semiconductors like SiC, Si, GaAs, and etc. Knowledge such as annealing property and microstructure of the deep traps could offer valuable information in developing the required device technology. For the case of ZnO, deep level traps and the relevant compensation were poorly understood in n-type and p-type doping of ZnO introduced by ion-implantation. This is in particular important for the asymmetry difficulty of p-type doping in ZnO, which is originated from the compensation of deep level traps having low formation energy and the low solubility of the dopants in ZnO [4]. DLTS have been employed to study the deep level defects in as-grown ZnO materials grown by different methods, and also those induced by particle irradiations. E1 (EC-0.12eV), E2 (EC-0.10eV), E3 (EC-0.30eV) and E4 (0.53-0.57eV below the EC) were the four deep level that usually found in as-grown ZnO materials [5,6]. Other deep traps like EC-0.20eV, EC-0.75eV, and EC-0.95eV were also observed in different ZnO materials [7,8]. However, their origins were poorly understood, speculative and controversial. Intrinsic defects in ZnO can be created by electron irradiation, O-implantation and Zn-implantation. The kinds of defects created depend on a number of factors, like the ion species, the energy of incident particle, and etc. For example, O-implantation and Zn-implantation would create intrinsic defects associated with O and Zn rich respectively. Electron irradiation with energy just above the threshold atomic displacement energy of the compound lattice AB would selectively displace the lighter atom [9]. Different kinds of intrinsic defects can thus be selectively created by choosing different particle species of irradiation, varying the particle incidence energy, and changing the irradiation condition. Aiming at understanding the origins of the DLTS signals, the following objectives were proposed in the present project. (1) Selectively creating the intrinsic defects associated with Zn-rich (Zn interstitial, O-vacancy, and Zn antisite), O-rich (O-interstitial, Zn-vacancy and O-antisite) by Zn and O-implantations. O-atom displacement related defects (i.e. O-vacancy and O-interstitial) can also be created by electron energy just above the threshold energy for atomic displacement. (2) Carrying out DLTS measurements on samples treated with different intrinsic defect creation processes. Characterizing the as found deep level traps including their activation energies, capture cross sections, thermal annealing behaviors and introduction rates by different kinds of irradiations. (3) Studying the microstructures of the as found deep traps. * References are in Appendix I |
| List of Research Outputs |
| Brauer G., Anwand W., Grambole D., Egger W., Sperr P., Beinik I., Wang L., Teichert C., Kuriplach J., Lang J., Zviagin S., Cizmar E., Ling F.C.C., Hsu Y.F., Xi Y., Chen X., Djurisic A. and Skorupa W., Characterization of ZnO nanostructures: A challenge to positron annihilation spectroscopy and other methods, physica status solidi (c). Weinheim, Wiley-VCH Verlag GmbH & Co., 2009, 6: 2556-2560. |
| Ding G., Ling F.C.C., Anwand W..., Brauer G... and Skorupa W..., Deep level transient spectroscopic study of nitrogen-implanted ZnO single crystal, The 37th International Symposium on Compound Semiconductors, May 31 to June 4 2010, Kagawa, Japan. 2010. |
| Fan J., Zhu C., Fung S.H.Y., Zhong Y.C., Wong K.S., Xie Z., Brauer G., Anwand W., Skorupa W., To C.K., Yang B., Beling C.D. and Ling F.C.C., Arsenic doped p-type zinc oxide films grown by radio frequency magnetron sputtering, Journal of Applied Physics. New York, American Institute of Physics, 2009, 106: 073709: 1-6. |
| Researcher : Liu B |
| List of Research Outputs |
| Ablikim M., Achasov M.N., An L., An Q., An Z.H., Bai J.Z., Ban Y., Berger N., Bian J.M., Boyko I., Briere R.A., Bytev V., Cai X., Cao G.F., Cao X.X., Chang J.F., Chelkov G., Chen G., Chen H.S., Chen J.C., Chen L.P., Chen M.L., Chen P., Chen S.J., Chen Y.B., Chu Y.P., Cronin-Hennessy D., Dai H.L., Dai J.P., Dedovich D., Deng Z.Y., Denysenko I., Destefanis M., Ding Y., Dong L.Y., Dong M.Y., Du S.X., Duan M.Y., Fang J., Feng C.Q., Fu C.D., Fu J.L., Gao Y., Geng C., Goetzen K., Gong W.X., Greco M., Grishin S., Gu Y.T., Guo A.Q., Guo L.B., Guo Y.P., Han S.Q., Harris F.A., He K.L., He M., He Z.Y., Heng Y.K., Hou Z.L., Hu H.M., Hu J.F., Hu T., Hu X.W., Huang B., Huang G.M., Huang J.S., Huang X.T., Huang Y.P., Ji C.S., Ji Q., Ji X.B., Ji X.L., Jia L.K., Jiang L.L., Jiang X.S., Jiao J.B., Jin D.P., Jin S., Komamiya S., Kuehn W., Lange S., Leung J.K.C., Li C., Li C., Li D.M., Li F., Li G., Li H.B., Li J., Li J.C., Li L., Li L., Li Q.J., Li W.D., Li W.G., Li X.L., Li X.N., Li X.Q., Li X.R., Li Y.X., Li Z.B., Liang H., Liang T.R., Liang Y.T., Liang Y.F., Liao G.R., Liao X.T., Liu B., Liu C.L., Liu C.X., Liu C.Y., Liu F.H., Liu F., Liu F., Liu G.C., Liu H., Liu H.B., Liu H.M., Liu H.W., Liu J., Liu J.P., Liu K., Liu K.Y., Liu Q., Liu S.B., Liu X.H., Liu Y.B., Liu Y.F., Liu Y.W., Liu Y., Liu Z.A., Lu G.R., Lu J.G., Lu Q.W., Lu X.R., Lu Y.P., Luo C.L., Luo M.X., Luo T., Luo X.L., Ma C.L., Ma F.C., Ma H.L., Ma Q.M., Ma X., Ma X.Y., Maggiora M., Mao Y.J., Mao Z.P., Min J., Mo X.H., Muchnoi N.Y., Nefedov Y., Ning F.P., Olsen S.L., Ouyang Q., Pelizaeus M., Peters K., Ping J.L., Ping R.G., Poling R., Pun J.C.S., Qi M., Qian S., Qiao C.F., Qiu J.F., Rong G., Ruan X.D., Sarantsev A., Shao M., Shen C.P., Shen X.Y., Sheng H.Y., Sonoda S., Spataro S., Spruck B., Sun D.H., Sun G.X., Sun J.F., Sun S.S., Sun X.D., Sun Y.J., Sun Y.Z., Sun Z.J., Sun Z.T., Tang C.J., Tang X., Tang X.F., Tian H.L., Toth D., Varner G.S., Wan X., Wang B.Q., Wang J.K., Wang K., Wang L.L., Wang L.S., Wang P., Wang P.L., Wang Q., Wang S.G., Wang X.D., Wang X.L., Wang Y.D., Wang Y.F., Wang Y.Q., Wang Z., Wang Z.G., Wang Z.Y., Wei D.H., Wen S.P., Wiedner U., Wu L.H., Wu N., Wu W., Wu Y.M., Wu Z., Xiao Z.J., Xie Y.G., Xu G.F., Xu G.M., Xu H., Xu M., Xu M., Xu X.P., Xu Y., Xu Z.Z., Xue Z., Yan L., Yan W.B., Yan Y.H., Yang H.X., Yang M., Yang P., Yang S.M., Yang Y.X., Ye M., Ye M.H., Yu B.X., Yu C.X., Yu L., Yuan C.Z., Yuan Y., Zeng Y., Zhang B.X., Zhang B.Y., Zhang C.C., Zhang D.H., Zhang H.H., Zhang H.Y., Zhang J.W., Zhang J.Y., Zhang J.Z., Zhang L., Zhang S.H., Zhang X.Y., Zhang Y., Zhang Y.H., Zhang Z.P., Zhao C., Zhao H.S., Zhao J.W., Zhao J.W., Zhao L., Zhao L., Zhao M.G., Zhao Q., Zhao S.J., Zhao T.C., Zhao X.H., Zhao Y.B., Zhao Z.G., Zhemchugov A., Zheng B., Zheng J.P., Zheng Y.H., Zheng Z.P., Zhong B., Zhong J., Zhou L., Zhou Z.L., Zhu C., Zhu K., Zhu K.J., Zhu Q.M., Zhu X.W., Zhu Y.S., Zhu Z.A., Zhuang J., Zou B.S., Zou J.H., Zuo J.X. and Zweber P., Branching fraction measurements of chi(c0) and chi(c2) to pi(0)pi(0) and eta eta, Physical Review D. New York, The American Physical Society, 2010, 81: 052005: 1-8. |
| Ablikim M., Achasov M.N., An L., An Q., An Z.H., Bai J.Z., Ban Y., Berger N., Bian J.M., Boyko I., Briere R.A., Bytev V., Cai X., Cao G.F., Cao X.X., Chang J.F., Chelkov G., Chen G., Chen H.S., Chen J.C., Chen L.P., Chen M.L., Chen P., Chen S.J., Chen Y.B., Chu Y.P., Cronin-Hennessy D., Dai H.L., Dai J.P., Dedovich D., Deng Z.Y., Denysenko I., Destefanis M., Ding Y., Dong L.Y., Dong M.Y., Du S.X., Duan M.Y., Fang J., Feng C.Q., Fu C.D., Fu J.L., Gao Y., Geng C., Goetzen K., Gong W.X., Greco M., Grishin S., Gu Y.T., Guo A.Q., Guo L.B., Guo Y.P., Han S.Q., Harris F.A., He K.L., He M., He Z.Y., Heng Y.K., Hou Z.L., Hu H.M., Hu J.F., Hu T., Hu X.W., Huang B., Huang G.M., Huang J.S., Huang X.T., Huang Y.P., Ji C.S., Ji Q., Ji X.B., Ji X.L., Jia L.K., Jiang L.L., Jiang X.S., Jiao J.B., Jin D.P., Jin S., Komamiya S., Kuehn W., Lange S., Leung J.K.C., Li C., Li C., Li D.M., Li F., Li G., Li H.B., Li J., Li J.C., Li L., Li L., Li Q.J., Li W.D., Li W.G., Li X.L., Li X.N., Li X.Q., Li X.R., Li Y.X., Li Z.B., Liang H., Liang T.R., Liang Y.T., Liang Y.F., Liao G.R., Liao X.T., Liu B., Liu C.L., Liu C.X., Liu C.Y., Liu F.H., Liu F., Liu F., Liu G.C., Liu H., Liu H.B., Liu H.M., Liu H.W., Liu J., Liu J.P., Liu K., Liu K.Y., Liu Q., Liu S.B., Liu X.H., Liu Y.B., Liu Y.F., Liu Y.W., Liu Y., Liu Z.A., Lu G.R., Lu J.G., Lu Q.W., Lu X.R., Lu Y.P., Luo C.L., Luo M.X., Luo T., Luo X.L., Ma C.L., Ma F.C., Ma H.L., Ma Q.M., Ma X., Ma X.Y., Maggiora M., Mao Y.J., Mao Z.P., Min J., Mo X.H., Muchnoi N.Y., Nefedov Y., Ning F.P., Olsen S.L., Ouyang Q., Pelizaeus M., Peters K., Ping J.L., Ping R.G., Poling R., Pun J.C.S., Qi M., Qian S., Qiao C.F., Qiu J.F., Rong G., Ruan X.D., Sarantsev A., Shao M., Shen C.P., Shen X.Y., Sheng H.Y., Sonoda S., Spataro S., Spruck B., Sun D.H., Sun G.X., Sun J.F., Sun S.S., Sun X.D., Sun Y.J., Sun Y.Z., Sun Z.J., Sun Z.T., Tang C.J., Tang X., Tang X.F., Tian H.L., Toth D., Varner G.S., Wan X., Wang B.Q., Wang J.K., Wang K., Wang L.L., Wang L.S., Wang P., Wang P.L., Wang Q., Wang S.G., Wang X.D., Wang X.L., Wang Y.D., Wang Y.F., Wang Y.Q., Wang Z., Wang Z.G., Wang Z.Y., Wei D.H., Wen S.P., Wiedner U., Wu L.H., Wu N., Wu W., Wu Y.M., Wu Z., Xiao Z.J., Xie Y.G., Xu G.F., Xu G.M., Xu H., Xu M., Xu M., Xu X.P., Xu Y., Xu Z.Z., Xue Z., Yan L., Yan W.B., Yan Y.H., Yang H.X., Yang M., Yang P., Yang S.M., Yang Y.X., Ye M., Ye M.H., Yu B.X., Yu C.X., Yu L., Yuan C.Z., Yuan Y., Zeng Y., Zhang B.X., Zhang B.Y., Zhang C.C., Zhang D.H., Zhang H.H., Zhang H.Y., Zhang J.W., Zhang J.Y., Zhang J.Z., Zhang L., Zhang S.H., Zhang X.Y., Zhang Y., Zhang Y.H., Zhang Z.P., Zhao C., Zhao H.S., Zhao J.W., Zhao J.W., Zhao L., Zhao L., Zhao M.G., Zhao Q., Zhao S.J., Zhao T.C., Zhao X.H., Zhao Y.B., Zhao Z.G., Zhemchugov A., Zheng B., Zheng J.P., Zheng Y.H., Zheng Z.P., Zhong B., Zhong J., Zhou L., Zhou Z.L., Zhu C., Zhu K., Zhu K.J., Zhu Q.M., Zhu X.W., Zhu Y.S., Zhu Z.A., Zhuang J., Zou B.S., Zou J.H., Zuo J.X. and Zweber P., Measurements of h(c) (P-1(1)) in psi ' decays, Physical Review Letters. New York, The American Physical Society, 2010, 104: 132002: 1-6. |
| Ablikim M., Achasov M.N., An L., An Q., An Z.H., Bai J.Z., Ban Y., Berger N., Bian J.M., Boyko I., Briere R.A., Bytev V., Cai X., Cao G.F., Cao X.X., Chang J.F., Chelkov G., Chen G., Chen H.S., Chen J.C., Chen L.P., Chen M.L., Chen P., Chen S.J., Chen Y.B., Chu Y.P., Cronin-Hennessy D., Dai H.L., Dai J.P., Dedovich D., Deng Z.Y., Denysenko I., Destefanis M., Ding Y., Dong L.Y., Dong M.Y., Du S.X., Duan M.Y., Fang J., Feng C.Q., Fu C.D., Fu J.L., Gao Y., Geng C., Goetzen K., Gong W.X., Greco M., Grishin S., Gu Y.T., Guo A.Q., Guo L.B., Guo Y.P., Han S.Q., Harris F.A., He K.L., He M., He Z.Y., Heng Y.K., Hou Z.L., Hu H.M., Hu J.F., Hu T., Hu X.W., Huang B., Huang G.M., Huang J.S., Huang X.T., Huang Y.P., Ji C.S., Ji Q., Ji X.B., Ji X.L., Jia L.K., Jiang L.L., Jiang X.S., Jiao J.B., Jin D.P., Jin S., Komamiya S., Kuehn W., Lange S., Leung J.K.C., Li C., Li C., Li D.M., Li F., Li G., Li H.B., Li J., Li J.C., Li L., Li L., Li Q.J., Li W.D., Li W.G., Li X.L., Li X.N., Li X.Q., Li X.R., Li Y.X., Li Z.B., Liang H., Liang T.R., Liang Y.T., Liang Y.F., Liao G.R., Liao X.T., Liu B., Liu C.L., Liu C.X., Liu C.Y., Liu F.H., Liu F., Liu F., Liu G.C., Liu H., Liu H.B., Liu H.M., Liu H.W., Liu J., Liu J.P., Liu K., Liu K.Y., Liu Q., Liu S.B., Liu X.H., Liu Y.B., Liu Y.F., Liu Y.W., Liu Y., Liu Z.A., Lu G.R., Lu J.G., Lu Q.W., Lu X.R., Lu Y.P., Luo C.L., Luo M.X., Luo T., Luo X.L., Ma C.L., Ma F.C., Ma H.L., Ma Q.M., Ma X., Ma X.Y., Maggiora M., Mao Y.J., Mao Z.P., Min J., Mo X.H., Muchnoi N.Y., Nefedov Y., Ning F.P., Olsen S.L., Ouyang Q., Pelizacus M., Peters K., Ping J.L., Ping R.G., Poling R., Pun J.C.S., Qi M., Qian S., Qiao C.F., Qiu J.F., Rong G., Ruan X.D., Sarantsev A., Shao M., Shen C.P., Shen X.Y., Sheng H.Y., Sonoda S., Spataro S., Spruck B., Sun D.H., Sun G.X., Sun J.F., Sun S.S., Sun X.D., Sun Y.J., Sun Y.Z., Sun Z.J., Sun Z.T., Tang C.J., Tang X., Tang X.F., Tian H.L., Toth D., Varner G.S., Wan X., Wang B.Q., Wang J.K., Wang K., Wang L.L., Wang L.S., Wang P., Wang P.L., Wang Q., Wang S.G., Wang X.D., Wang X.L., Wang Y.D., Wang Y.F., Wang Y.Q., Wang Z., Wang Z.G., Wang Z.Y., Wei D.H., Wen S.P., Wiedner U., Wu L.H., Wu N., Wu Y.M., Wu Z., Xiao Z.J., Xie Y.G., Xu G.F., Xu G.M., Xu H., Xu M., Xu M., Xu X.P., Xu Y., Xu Z.Z., Xue Z., Yan L., Yan W.B., Yan Y.H., Yang H.X., Yang M., Yang P., Yang S.M., Yang Y.X., Ye M., Ye M.H., Yu B.X., Yu C.X., Yu L., Yuan C.Z., Yuan Y., Zeng Y., Zhang B.X., Zhang B.Y., Zhang C.C., Zhang D.H., Zhang H.H., Zhang H.Y., Zhang J.W., Zhang J.Y., Zhang J.Z., Zhang L., Zhang S.H., Zhang X.Y., Zhang Y., Zhang Y.H., Zhang Z.P., Zhao C., Zhao H.S., Zhao J.W., Zhao J.W., Zhao L., Zhao L., Zhao M.G., Zhao Q., Zhao S.J., Zhao T.C., Zhao X.H., Zhao Y.B., Zhao Z.G., Zhemchugov A., Zheng B., Zheng J.P., Zheng Y.H., Zheng Z.P., Zhong B., Zhong J., Zhou L., Zhou Z.L., Zhu C., Zhu K., Zhu K.J., Zhu Q.M., Zhu X.W., Zhu Y.S., Zhu Z.A., Zhuang J., Zou B.S., Zou J.H., Zuo J.X. and Zweber P., Observation of a p(p)over-bar mass threshold enhancement in psi ' -> pi(+)pi(-)J/psi(J/psi -> gamma p(p)over-bar) decay, Chinese Physics C . Chinese Physical Soc, 2010, 34: 421-426. |
| Researcher : Liu H |
| List of Research Outputs |
| Gao J., Hu F. and Liu H., Field effects in thin films of manganites using a planar field effect configuration, Journal of Superconductivity and Novel Magnetism. Springer, 2010, 23: 855-857. |
| Researcher : Lu H |
| List of Research Outputs |
| Dai J., Lu H., Yang C., Shen S.Q., Zhang F.C. and Cui X., Magnetoelectric photocurrent generated by direct interband transitions in InGaAs/InAlAs two-dimensional electron gas, Physical Review Letters. New York, The American Physical Society, 2010, 104: 246601: 1-4. |
| Lu H. and Shen S.Q., Detecting and switching magnetization of Stoner nanograin in nonlocal spin valve, Physical Review B. New York, The American Physical Society, 2009, 80: 094401: 1-15. |
| Lu H., Shan W., Yao W., Niu Q. and Shen S.Q., Massive Dirac fermions and spin physics in an ultrathin film of topological insulator, Physical Review B. The American Physical Society, 2010, 81: 115407: 1-7. |
| Shan W., Lu H. and Shen S.Q., Effective continuous model for surface states and thin films of three-dimensional topological insulators, New Journal of Physics. Bristol, IOP Publishing Limited, 2010, 12: 043048: 1-23. |
| Researcher : Luo Z |
| List of Research Outputs |
| Luo Z. and Gao J., Anomalous temperature and magnetic field dependences of current-voltage characteristics in Pr0.6Ca0.4MnO3/Nb-doped SrTiO3 heterojunctions, Journal of Physics D: Applied Physics. Bristol, IOP Publishing Limited, 2010, 43: 175003: 1-6. |
| Researcher : Ma PN |
| List of Research Outputs |
| Ma P.N., Numerical exact simulations of actual-size bosonic optical lattice systems. Hong Kong, The University of Hong Kong, 2009, 1-54. |
| Researcher : Nakashima J |
| Project Title: | Observational Study of Red Supergiants Embedded in Massive Open Star Clusters |
| Investigator(s): | Nakashima J, Kwok S, Zhang Y |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 07/2008 |
| Completion Date: | 07/2010 |
| Abstract: |
| V-1. Background of Research V-1-1. Work done by others Mass-loss phenomena of red supergiants (RSGs), the evolved massive stars in the core helium-burning phase, play a key role in a wide variety of important astrophysical problems. To understand the mass-loss phenomena of RSGs, ultimately we have to obtain the mass-loss rate as a function of time, direction and other stellar parameters like initial metallicity, initial mass, binarity and etc. Unfortunately, it is rather difficult for the isolated RSGs to obtain such stellar parameters. In contrast, RSGs lying in galactic open clusters provide us a precious chance to investigate the mass-loss of RSGs under the constraints of uniform initial metallicity and distance, while being close enough to observe in detail. Even the initial mass of RSGs may be estimated if we derive the HR-diagram of the open cluster. However, the number of such RSGs known in galactic open clusters is quite limited. In recent several years, above situation has been changing due to the advent of new infrared systematic surveys epitomized by the Spitzer/GLIMPSE, 2MASS, and MSX (Egan et al. 1999; Benjamin et al. 2003; Cutri et al. 2003). These surveys (especially, the Spitzer/GLIMPSE survey) found a number of highly reddened open clusters deeply embedded in the galactic plane region thanks to its remarkable high sensitivity and high angular resolution at the mid-infrared wavelength (e.g., Mercer et al. 2005). In such newly found open clusters, a number of RSGs candidates have been found. For example, Nakaya et al. (2001) found 10 candidates for RSGs in a highly reddened open cluster found by their I-band systematic survey (Stephenson et al. 1990). Similarly, Figer et al. (2006) and Davies et al. (2007) respectively found 14 and 26 candidates for RSGs in highly reddened open clusters newly found in 2MASS images (Bica et al. 2003). Thus, the current important outstanding issues in the RSGs study are (1) to securely identify RSGs in such newly found open clusters with a reliable method, and (2) to obtain fundamental stellar parameters of RSGs in open clusters (for example, distance and mass-loss rates), so that we can open a new door for statistical studies on RSGs. V-1-2. Work done by us The SiO maser emission, the non-thermally amplified molecular rotational-line of the SiO molecule (Reid 1981; Elitzur 1992), is usually detected only in evolved stars such as RSGs. Thus, we can identify RSGs in an open cluster once we detect SiO maser emission toward a member star of an open cluster. To confirm the feasibility of the this method, last year we searched the SiO maser line (J=1-0, v=1&2) toward 14 RSG candidates in a young open cluster recently found by Figer et al. (2006) using the Nobeyama 45 m telescope (Nakashima & Deguchi 2006). Consequently, we detected 4 SiO maser sources. Figure 1 shows a 2MASS infrared image of the observed cluster and spectra of the detected SiO maser lines. With the radial velocities obtained by this SiO maser observation, we calculated the kinetic distances to the clusters (~6.5 kpc) on the assumption of the circular rotation of the galaxy, and confirmed with the obtained distances, that the absolute infrared luminosity of the SiO maser sources is consistent with RSGs. V-1-3. Goals of this project The goals of this project are as follows: (1) Red supergiants (RSGs) in young open clusters exhibit a uniform distances and initial metallicity; this situation provides us a precious chance to study RSGs. However, the number of RSGs ever known in galactic open clusters is quite limited. In this research, we will identify a number of new RSGs in newly found galactic open clusters by observing the SiO and OH maser emission, so that we can drastically increase the number of known RSGs in galactic open clusters. (2) We will try to obtain fundamental stellar parameters of the identified RSGs. Specifically we will obtain kinematical distances to RSGs using radial velocities obtained from maser observations, and try to estimate mass-loss rates of the RSGs by observing their CO and OH maser lines. (3) We will map the gas component of open clusters harboring RSGs in the CO rotational line, so that we can reveal the kinematics of the gas component. Through the CO observation, we can investigate how the RSG mass-loss phenomena affect the gas component of open clusters. The results of this CO mapping observation enable us to consider the feasibility of future radio interferometric observations using ALMA and CARMA. |
| Project Title: | Observational Study of Red Supergiants Embedded in Galactic Young Open Clusters |
| Investigator(s): | Nakashima J, Kwok S |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2008 |
| Abstract: |
| 1) RSGs in young open clusters exhibit a uniform distances and initial metallicity; this situation provides us a precious chance to study RSGs. However, the number of RSGs ever known in galactic open clusters is quite limited. In this research, we will identify a number of RSGs in newly found galactic open clusters by observing the SiO and OH maser emission, so that we can drastically increase the number of known RSGs in galactic open clusters. 2) We will try to obtain fundamental stellar parameters of the identified RSGs. Specifically we will obtain kinematical distances to RSGs using radial velocities obtained from maser observations, and try to estimate mass-loss rates of the RSGs by observing their CO and OH maser lines. 3) We will map the gas component of open clusters harboring RSGs in the CO rotational line, so that we can reveal the kinematics of the gas component. Through the CO observation, we can investigate how the RSG mass-loss phenomena affect the gas component of open clusters. The results of this CO mapping observation enable us to consider the feasibility of future radio interferometric observations using ALMA and CARMA. |
| Project Title: | Radio Interferometric Observations of Post-AGB Stars and Proto-Planetary Nebulae |
| Investigator(s): | Nakashima J |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2009 |
| Abstract: |
| 1) We will reveal morpho-kinematic properties of water fountains and 21-micron sources through interferometric observations in the maser and CO lines. 2) We will obtain the dynamical timescales of key kinematic components (i.e., torus, jet and expanding sphere) by creating a morpho-kinematic model with Shape, and with the obtained dynamical timescales, we will constrain theoretical models explaining the formation of jet and torus. 3) We will bring up, at least, 1-2 Mphil/PhD students, in the duration of this project. 4) We will build up a good & tight partnership with foreign researchers and institutions, especially with the Kagoshima University and Nobeyama Radio Observatory, to consolidate the capability of astronomical research in HKU. 5) We will build up a good educational environment by hiring a senior research assistant, who contributes the observations and data analyses and also stimulates students and other group members. |
| List of Research Outputs |
| Deguchi S., Matsunaga N., Takahashi S., Kuno N. and Nakashima J., Dying SiO masers in the V407 Cyg system, The Astronomer's Telegram, #2519. 2010, 2519. |
| Deguchi S., Nakashima J., Zhang Y., Chong S.N., Koike K. and Kwok S., SiO and H2O maser observations of red supergiants in star clusters embedded in the galactic disk, Publications of the Astronomical Society of Japan. Astronomical Society of Japan, 2010, 62: 391-407. |
| He J.H., Imai H., Hasegawa T., Campbell S. and Nakashima J., CO observations of water fountain stars, The Frontier of Interstellar Medium - 40th Anniversary of the Discovery of CO in ISM. 2010. |
| Hsia C. and Nakashima J., Telescope Time of Lulin 40 cm Telescope (Project Title: Photometric monitoring for an unique nova V407 Cyg), Lulin Observatory. 2010. |
| Imai H., He J.H., Nakashima J., Ukita N., Deguchi S. and Koning N., CO J=3-2 emission from the "water fountain" sources IRAS 16342-3814 and IRAS 18286-0959, Publications of the Astronomical Society of Japan. Astronomical Soc Japan, 2009, 61: 1365-1372. |
| Imai H., Nakagawa A., Nagayama T., Nakashima J., Deguch S. and Kamohara R., First VLBI Observation of a Circumstellar Envelope in the SiO v=3, J=1-0 Line, Astronomical Society of Japan Autumn Meeting (September 2009) at Yamaguchi Univ.. 2009. |
| Imai H., Yung H.K.B., Nakashima J., Deguchi S., Diamond P.J. and Kwok S., High Velocity Precessing Jets from the Water Fountain IRAS 18286−0959 Revealed by VLBA Observations, East Asia VLBI Workshop 2010. . |
| Imai H., Nakashima J., Deguchi S., Yamauchi A., Nakagawa A. and Nagayama T., Japanese VLBI network mapping of SiO nu=3 J=1-0 maser emission in W Hydrae, Publications of the Astronomical Society of Japan. Astronomical Soc Japan, 2010, 62: 431-439. |
| Nakashima J., SMA Observations of Protoplanetary Nebulae and Planetary Nebulae and Perspective for ALMA, In: Hideki Izumiura, ALMA Workshop - Evolved Stars -. 2009. |
| Nakashima J., Deguchi S., Imai H., Kwok S., Koning N., Yung H.K.B., Zhang Y. and Chong S.N., Telescope Time of CARMA (Project Title: CO Mapping of the Water Fountain Object IRAS 18286-0959) , Combined Array for Research in Millimeter-wave Astronomy (CARMA). 2010. |
| Nakashima J., Kwok S., Zhang Y., Hsia C., Chong S.N., Yung B.H.K., Koning N. and Deguchi S., Telescope Time of the NRO 45m Telescope (Project Title: 3D Structure of the Helix: Verification of the Bicone Model), Nobeyama Radio Observatory, National Astronomical Observatory of Japan. 2010. |
| Zhang Y., Nakashima J., Kwok S., Chong S.N. and Deguchi S., Telescope Time of the NRO 45m Telescope (Project Title: A Spectral Line Survey in the 7mm Window toward the Highly Evolved Carbon Star CIT 6), Nobeyama Radio Observatory, National Astronomical Observatory of Japan. 2010. |
| Researcher : Ng A |
| List of Research Outputs |
| Wang X.Z., Wang Q.W., Yan L., Wong W.Y., Cheung K.Y., Ng A., Djurisic A. and Chan W.K., Very-low-bandgap metallopolyynes of platinum with a cyclopentadithiophenone ring for organic solar cells absorbing down to the near-infrared spectral region, Macromolecular Rapid Communications. Weinheim, WILEY-VCH Verlag GmbH & Co. KGaA, 2010, 31: 861-867. |
| Researcher : Ng AMC |
| Project Title: | International Conference on Nanomaterials: Synthesis, Characterization and Application (ICN 2010) ZnO nanomaterials: growth and applications |
| Investigator(s): | Ng AMC |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 04/2010 |
| Completion Date: | 04/2010 |
| Abstract: |
| N/A |
| List of Research Outputs |
| Djurisic A., Ng A.M.C. and Chen X., ZnO nanostructures for optoelectronics: Material properties and device applications, Progress in Quantum Electronics. Elsevier Ltd., 2010, 34: 191-259. |
| Tong W.Y., Chen H.Y., Djurisic A., Ng A.M.C., Wang H., Gwo S. and Chan W.K., Infrared photoluminescence from α- and β-copper phthalocyanine nanostructures, Optical Materials. Amsterdam, Elsevier B.V., 2010, 32: 924-927. |
| Researcher : Ng MCA |
| List of Research Outputs |
| Chen X., Ng M.C.A., Fang F., Djurisic A., Chan W.K., Tam H.L., Cheah K.W., Fong P.W.K., Lui H.F. and Surya C., The influence of the ZnO seed layer on the ZnO nanorod/GaN LEDs, Journal of the Electrochemical Society. The Electrochemical Society, 2010, 157: H308-H311. |
| Ng M.C.A., Xi Y., Hsu Y.F., Djurisic A., Chan W.K., Gwo S., Tam H.L., Cheah K.W., Fong P.W.K., Lui H.F. and Surya C., GaN/ZnO nanorod light emitting diodes with different emission spectra, Nanotechnology. Bristol, IOP Publishing Limited, 2009, 20: 445201: 1-8. |
| Ng M.C.A., Light emitting diodes based on ZnO nanorods. Hong Kong, The University of Hong Kong, 2010, 1-112. |
| Researcher : Pun JCS |
| Project Title: | Radio telescope for physics and astronomy teaching and research |
| Investigator(s): | Pun JCS |
| Department: | Physics |
| Source(s) of Funding: | Leung Kau Kui Research and Teaching Endowment Fund - Teaching Grants |
| Start Date: | 05/2004 |
| Abstract: |
| Establish the first radio astronomical telescope in Hong Kong, strengthening the leadership of HKU on astronomy education; provide students with an all-rounded training in astronomy education; lay the foundation of radio astronomy research in Hong Kong; strengthen the role of HKU as the leading public voice on issues related to astronomy. |
| Project Title: | Understanding the nature of supernova remnant 1987A |
| Investigator(s): | Pun JCS |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2006 |
| Completion Date: | 08/2009 |
| Abstract: |
| (1) Supernova 1987A (SN 1987A) is a once-in-a-lifetime event which has not only provided the best-observed death of a star, but also the first-observed birth of a supernova remnant (SNR) in real time. We propose to study the SNR 1987A in detail to understand the explosion mechanism of the progenitor star, the final stages of stellar evolution, and the transfer of materials and energy of the exploded star to the interstellar environment. (2) The main goal of this project is to use the data taken from the Hubble Space Telescope (HST) to understand the nature of the various physical components of SN 1987A, including the inner explosion debris, the circumstellar gas system, and the interaction underway between the two. The high spatial resolution of the HST data allows the different components to be resolved and can thus be studied in detail separately. (3) We plan to study the evolution of the SN 1987A debris, important for understanding the dynamics and nature of the explosion itself. HST allows for the first time a young supernova explosion debris to be resolved and we hope to study its detailed structure. In addition, we hope to monitor the photometry energy output in the hope of providing a better limit of the energy output of the central compact object left behind from the supernova explosion, thus constraining its nature (e.g. is there a surviving companion, neutron star, or pulsar?). (4) One of the most exciting mysteries of SN 1987A is the circumstellar three-ring system. The rings are gas ejected by the progenitor star during the last phase of stellar evolution. They were ionized by the supernova shock breakout and have been recombining since. In addition to studying the bright equatorial inner ring, we propose to investigate the physical structure from the outer rings, which are only entirely resolved in the HST data. The results may provide insights to the mass loss history of the progenitor in the final stage of its evolution, from which the nature of the progenitor star can be deduced. (5) A recent development of the SN 1987A system is the detection of shock interaction between the fastest moving materials of the debris and the circumstellar gas, thus becoming a supernova remnant (SNR). SNR 1987A provides the first opportunity for this process to be monitored in real time and we plan to study the emission from the shock interaction. HST observations are useful for studying the temporal evolution of the various components of the interaction in detail. Combining with observations in other wavelengths, in particular radio and X-ray, we hope to come up with a more coherent picture of the physics involved. The results may shed light on processes such as induced stellar formations and the chemical enrichment of the universe. |
| Project Title: | Radio Interferometry System for Physics and Astronomy Teaching and Research |
| Investigator(s): | Pun JCS |
| Department: | Physics |
| Source(s) of Funding: | Leung Kau Kui Research and Teaching Endowment Fund - Teaching Grants |
| Start Date: | 09/2007 |
| Completion Date: | 08/2009 |
| Abstract: |
| We propose to establish the first radio interferometry facility for astronomy teaching and research in Hong Kong. With the support of a previous Leung Kau Kui Research and Teaching Endowment Fund, we have constructed the very first radio astronomical telescope in Hong Kong. Using this facility, students have the opportunities to be exposed to astronomy in the radio wavelength, the only other fully-accessible radiation range from the universe apart from the visual wavelengths. Currently HKU is the only local institution offering a systematic training in the field of astronomy. We are now actively planning to offer astronomy as a major, further developing this very popular science subject amongst students as a rigorous academic discipline. To strengthen the leadership of HKU on astronomy education and to provide an all-rounded training in astronomy to students, we need to expand the existing laboratory tools. One significant area of weakness that exists in our curriculum is the lack of training in the field of astronomical interferometry. Interferometry is the technique of using multiple receiving dishes to achieve high resolution data in replacement of building a single larger dish. This cost-effective technique is one of the foundation blocks of modern radio astronomy and it is essential that we are equipped with this tool to provide a complete and all-rounded training in observational astronomy to students, especially those taking astronomy as their major or minor options. In addition to its educational values, the radio interferometry array will lay the cornerstone for radio astronomy research in Hong Kong. While the crowded living environment in Hong Kong prohibits research grade observations to be carried out in visible light, there is no such limitation in radio bandwidths. In the long run, we hope to link up with the National Astronomical Observatories radio stations in Beijing, Shanghai, and Urumqi to establish the first Chinese radio interferometer. The total budget requested is $100,000, including the purchase of the satellite dish, telescope mount, digital receivers, data acquisition system, and data storage devices, together with the hiring of a part-time technical staff to assist with the installation of the radio telescope and the construction of the adding interferometer. |
| Project Title: | Simulations and Data Analysis of Neutron Production inside the Aberdeen Tunnel underground laboratory |
| Investigator(s): | Pun JCS, Leung JKC |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 10/2007 |
| Abstract: |
| To develop the data archiving system and the offline analysis programs to measure the muon-induced neutron production of the Aberdeen Tunnel experiment. To perform simulations to constrain and optimize the design parameters for the various components of neutron detector to be installed inside the Aberdeen Laboratory. To perform simulations to understand the experimental background of the Aberdeen Tunnel experiment, including that from the radioactive elements of the surrounding rocks and the experimental components, to aid for the design of the configuration and thickness of the shielding system. To perform simulations on the efficiency of the calibration system of the Aberdeen Tunnel experiment. To verify accuracy of simulation programs by comparing with experimental results on the muon-induced neutron production in an underground laboratory. |
| Project Title: | Monitoring the Night Sky Brightness of Sai Kung |
| Investigator(s): | Pun JCS |
| Department: | Physics |
| Source(s) of Funding: | Small Project Funding |
| Start Date: | 01/2008 |
| Completion Date: | 12/2009 |
| Abstract: |
| The brightness level of the night sky depends on many factors. Some have natural causes, such as the phase from the moon and light from the Galaxy. Some are meteorological in nature, such as the thickness of cloud, temperature, and humidity. However, many others have artificial origins, such as the density of particulates and aerosol molecules due to air pollution, and, last but not least, the stray light coming from artificial outdoor lighting due to light pollution. In order to properly understand the condition of light pollution in Hong Kong, we propose to conduct the first long-term monitor of the night sky condition using standard photometry techniques widely adopted worldwide as a reliable method to study the problem [e.g., 1,2,3]. The PI of this proposal has been working on a pilot project to measure the sky brightness of Hong Kong since 2003, using the technique of astronomical photometry. Pictures of the night sky were taken with telescopes and astronomical CCD cameras that are specially designed to photograph dark objects. We have measured the brightness of the night sky in the University of Hong Kong campus, an urban setting, and in two countryside settings in the Sai Kung High Island Reservoir and Shui Hau in the Lantau Island South. Preliminary results from over 40 sets of data over 4 years indicate that the darkest urban night sky observable is at least 30 times brighter than the countryside counterpart. This shows that the heavy use of lighting in the city is indeed polluting the night sky. It was also found that the night sky is significantly brighter in early evening before 12am than in late night after 12am within the same night of measurement, reflecting the effects of human activities. While we have been able to roughly determine the effects of artificial lighting by comparing the night sky brightness measurements between a few urban and countryside locations, the data is insufficient for providing a complete picture of the condition of the light pollution in Hong Kong. The major problem is that the observations were only sparsely made because of the heavy time commitment required. It is important to design a system to automatically obtain observing data. We propose to monitor the brightness of the night sky over a 6-month period using imaging data taken from a CCD camera connected to a small telescope which in turn is mounted to the Hong Kong Space Museum Telescope (SPMT) in Sai Kung. Upon completion around the end of 2007, the SPMT is expected to be fully programmable remotely over the internet and its operation will be fully automatic. With scheduling of the SPMT known in advance from the Hong Kong Space Museum, we will be able to open the CCD camera for collecting night sky quality data whenever the SPMT is in operation. We propose to use the automatic data analysis system proposed by F. Patat [2] to determine the night sky brightness from the large amount of data expected to be collected over the 6-month period. Long-term variations of the night sky brightness can be monitored and analyzed in the hope that effects from air pollution and light pollution can be isolated from the natural and meteorological factors. [1] Pilachowski, C.A., et al. 1989, Publications of the Astronomical Society of the Pacific, 101, 707 [2] Patat, F 2003, Astronomy and Astrophysics, 401, 797 [3] Krisciunas, K., et al. 2007, Publications of the Astronomical Society of the Pacific, in press (arXiv:0705.113) |
| Project Title: | Study of Supersoft X-Ray Sources and Quasisoft X-Ray Sources in the Milky Way and the Magellanic Clouds |
| Investigator(s): | Pun JCS |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 01/2010 |
| Abstract: |
| 1) To develop mission-specific selection criteria and algorithms for supersoft X-ray sources (SSS) and quasisoft X-ray sources (QSS), together referred to as very soft X-ray sources (VSS); 2) To search for VSS in the Milky Way and the Magellanic Clouds using archival catalogues of X-ray missions; 3) To study properties of VSS selected, including temperature and luminosity range, spatial distribution, and time variability, and compare them with VSS identified in external galaxies; 4) To identify counterparts of VSS candidates in other wavelengths which not only will be helpful for removing foreground and background objects from the list, but also for understanding the nature of the binary system; 5) To provide observational details for evaluating the different physical models of SSS and QSS |
| Project Title: | 11th High Energy Astrophysics Division Meeting (HEAD 2010) Studies of Supersoft X-ray Sources (SSS) and Quasisoft X-ray Sources (QSS) in the Milky Way and Magellanic Clouds |
| Investigator(s): | Pun JCS |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 03/2010 |
| Completion Date: | 03/2010 |
| Abstract: |
| N/A |
| List of Research Outputs |
| Ablikim M., Achasov M.N., An L., An Q., An Z.H., Bai J.Z., Ban Y., Berger N., Bian J.M., Boyko I., Briere R.A., Bytev V., Cai X., Cao G.F., Cao X.X., Chang J.F., Chelkov G., Chen G., Chen H.S., Chen J.C., Chen L.P., Chen M.L., Chen P., Chen S.J., Chen Y.B., Chu Y.P., Cronin-Hennessy D., Dai H.L., Dai J.P., Dedovich D., Deng Z.Y., Denysenko I., Destefanis M., Ding Y., Dong L.Y., Dong M.Y., Du S.X., Duan M.Y., Fang J., Feng C.Q., Fu C.D., Fu J.L., Gao Y., Geng C., Goetzen K., Gong W.X., Greco M., Grishin S., Gu Y.T., Guo A.Q., Guo L.B., Guo Y.P., Han S.Q., Harris F.A., He K.L., He M., He Z.Y., Heng Y.K., Hou Z.L., Hu H.M., Hu J.F., Hu T., Hu X.W., Huang B., Huang G.M., Huang J.S., Huang X.T., Huang Y.P., Ji C.S., Ji Q., Ji X.B., Ji X.L., Jia L.K., Jiang L.L., Jiang X.S., Jiao J.B., Jin D.P., Jin S., Komamiya S., Kuehn W., Lange S., Leung J.K.C., Li C., Li C., Li D.M., Li F., Li G., Li H.B., Li J., Li J.C., Li L., Li L., Li Q.J., Li W.D., Li W.G., Li X.L., Li X.N., Li X.Q., Li X.R., Li Y.X., Li Z.B., Liang H., Liang T.R., Liang Y.T., Liang Y.F., Liao G.R., Liao X.T., Liu B., Liu C.L., Liu C.X., Liu C.Y., Liu F.H., Liu F., Liu F., Liu G.C., Liu H., Liu H.B., Liu H.M., Liu H.W., Liu J., Liu J.P., Liu K., Liu K.Y., Liu Q., Liu S.B., Liu X.H., Liu Y.B., Liu Y.F., Liu Y.W., Liu Y., Liu Z.A., Lu G.R., Lu J.G., Lu Q.W., Lu X.R., Lu Y.P., Luo C.L., Luo M.X., Luo T., Luo X.L., Ma C.L., Ma F.C., Ma H.L., Ma Q.M., Ma X., Ma X.Y., Maggiora M., Mao Y.J., Mao Z.P., Min J., Mo X.H., Muchnoi N.Y., Nefedov Y., Ning F.P., Olsen S.L., Ouyang Q., Pelizaeus M., Peters K., Ping J.L., Ping R.G., Poling R., Pun J.C.S., Qi M., Qian S., Qiao C.F., Qiu J.F., Rong G., Ruan X.D., Sarantsev A., Shao M., Shen C.P., Shen X.Y., Sheng H.Y., Sonoda S., Spataro S., Spruck B., Sun D.H., Sun G.X., Sun J.F., Sun S.S., Sun X.D., Sun Y.J., Sun Y.Z., Sun Z.J., Sun Z.T., Tang C.J., Tang X., Tang X.F., Tian H.L., Toth D., Varner G.S., Wan X., Wang B.Q., Wang J.K., Wang K., Wang L.L., Wang L.S., Wang P., Wang P.L., Wang Q., Wang S.G., Wang X.D., Wang X.L., Wang Y.D., Wang Y.F., Wang Y.Q., Wang Z., Wang Z.G., Wang Z.Y., Wei D.H., Wen S.P., Wiedner U., Wu L.H., Wu N., Wu W., Wu Y.M., Wu Z., Xiao Z.J., Xie Y.G., Xu G.F., Xu G.M., Xu H., Xu M., Xu M., Xu X.P., Xu Y., Xu Z.Z., Xue Z., Yan L., Yan W.B., Yan Y.H., Yang H.X., Yang M., Yang P., Yang S.M., Yang Y.X., Ye M., Ye M.H., Yu B.X., Yu C.X., Yu L., Yuan C.Z., Yuan Y., Zeng Y., Zhang B.X., Zhang B.Y., Zhang C.C., Zhang D.H., Zhang H.H., Zhang H.Y., Zhang J.W., Zhang J.Y., Zhang J.Z., Zhang L., Zhang S.H., Zhang X.Y., Zhang Y., Zhang Y.H., Zhang Z.P., Zhao C., Zhao H.S., Zhao J.W., Zhao J.W., Zhao L., Zhao L., Zhao M.G., Zhao Q., Zhao S.J., Zhao T.C., Zhao X.H., Zhao Y.B., Zhao Z.G., Zhemchugov A., Zheng B., Zheng J.P., Zheng Y.H., Zheng Z.P., Zhong B., Zhong J., Zhou L., Zhou Z.L., Zhu C., Zhu K., Zhu K.J., Zhu Q.M., Zhu X.W., Zhu Y.S., Zhu Z.A., Zhuang J., Zou B.S., Zou J.H., Zuo J.X. and Zweber P., Branching fraction measurements of chi(c0) and chi(c2) to pi(0)pi(0) and eta eta, Physical Review D. New York, The American Physical Society, 2010, 81: 052005: 1-8. |
| Ablikim M., Achasov M.N., An L., An Q., An Z.H., Bai J.Z., Ban Y., Berger N., Bian J.M., Boyko I., Briere R.A., Bytev V., Cai X., Cao G.F., Cao X.X., Chang J.F., Chelkov G., Chen G., Chen H.S., Chen J.C., Chen L.P., Chen M.L., Chen P., Chen S.J., Chen Y.B., Chu Y.P., Cronin-Hennessy D., Dai H.L., Dai J.P., Dedovich D., Deng Z.Y., Denysenko I., Destefanis M., Ding Y., Dong L.Y., Dong M.Y., Du S.X., Duan M.Y., Fang J., Feng C.Q., Fu C.D., Fu J.L., Gao Y., Geng C., Goetzen K., Gong W.X., Greco M., Grishin S., Gu Y.T., Guo A.Q., Guo L.B., Guo Y.P., Han S.Q., Harris F.A., He K.L., He M., He Z.Y., Heng Y.K., Hou Z.L., Hu H.M., Hu J.F., Hu T., Hu X.W., Huang B., Huang G.M., Huang J.S., Huang X.T., Huang Y.P., Ji C.S., Ji Q., Ji X.B., Ji X.L., Jia L.K., Jiang L.L., Jiang X.S., Jiao J.B., Jin D.P., Jin S., Komamiya S., Kuehn W., Lange S., Leung J.K.C., Li C., Li C., Li D.M., Li F., Li G., Li H.B., Li J., Li J.C., Li L., Li L., Li Q.J., Li W.D., Li W.G., Li X.L., Li X.N., Li X.Q., Li X.R., Li Y.X., Li Z.B., Liang H., Liang T.R., Liang Y.T., Liang Y.F., Liao G.R., Liao X.T., Liu B., Liu C.L., Liu C.X., Liu C.Y., Liu F.H., Liu F., Liu F., Liu G.C., Liu H., Liu H.B., Liu H.M., Liu H.W., Liu J., Liu J.P., Liu K., Liu K.Y., Liu Q., Liu S.B., Liu X.H., Liu Y.B., Liu Y.F., Liu Y.W., Liu Y., Liu Z.A., Lu G.R., Lu J.G., Lu Q.W., Lu X.R., Lu Y.P., Luo C.L., Luo M.X., Luo T., Luo X.L., Ma C.L., Ma F.C., Ma H.L., Ma Q.M., Ma X., Ma X.Y., Maggiora M., Mao Y.J., Mao Z.P., Min J., Mo X.H., Muchnoi N.Y., Nefedov Y., Ning F.P., Olsen S.L., Ouyang Q., Pelizaeus M., Peters K., Ping J.L., Ping R.G., Poling R., Pun J.C.S., Qi M., Qian S., Qiao C.F., Qiu J.F., Rong G., Ruan X.D., Sarantsev A., Shao M., Shen C.P., Shen X.Y., Sheng H.Y., Sonoda S., Spataro S., Spruck B., Sun D.H., Sun G.X., Sun J.F., Sun S.S., Sun X.D., Sun Y.J., Sun Y.Z., Sun Z.J., Sun Z.T., Tang C.J., Tang X., Tang X.F., Tian H.L., Toth D., Varner G.S., Wan X., Wang B.Q., Wang J.K., Wang K., Wang L.L., Wang L.S., Wang P., Wang P.L., Wang Q., Wang S.G., Wang X.D., Wang X.L., Wang Y.D., Wang Y.F., Wang Y.Q., Wang Z., Wang Z.G., Wang Z.Y., Wei D.H., Wen S.P., Wiedner U., Wu L.H., Wu N., Wu W., Wu Y.M., Wu Z., Xiao Z.J., Xie Y.G., Xu G.F., Xu G.M., Xu H., Xu M., Xu M., Xu X.P., Xu Y., Xu Z.Z., Xue Z., Yan L., Yan W.B., Yan Y.H., Yang H.X., Yang M., Yang P., Yang S.M., Yang Y.X., Ye M., Ye M.H., Yu B.X., Yu C.X., Yu L., Yuan C.Z., Yuan Y., Zeng Y., Zhang B.X., Zhang B.Y., Zhang C.C., Zhang D.H., Zhang H.H., Zhang H.Y., Zhang J.W., Zhang J.Y., Zhang J.Z., Zhang L., Zhang S.H., Zhang X.Y., Zhang Y., Zhang Y.H., Zhang Z.P., Zhao C., Zhao H.S., Zhao J.W., Zhao J.W., Zhao L., Zhao L., Zhao M.G., Zhao Q., Zhao S.J., Zhao T.C., Zhao X.H., Zhao Y.B., Zhao Z.G., Zhemchugov A., Zheng B., Zheng J.P., Zheng Y.H., Zheng Z.P., Zhong B., Zhong J., Zhou L., Zhou Z.L., Zhu C., Zhu K., Zhu K.J., Zhu Q.M., Zhu X.W., Zhu Y.S., Zhu Z.A., Zhuang J., Zou B.S., Zou J.H., Zuo J.X. and Zweber P., Measurements of h(c) (P-1(1)) in psi ' decays, Physical Review Letters. New York, The American Physical Society, 2010, 104: 132002: 1-6. |
| Ablikim M., Achasov M.N., An L., An Q., An Z.H., Bai J.Z., Ban Y., Berger N., Bian J.M., Boyko I., Briere R.A., Bytev V., Cai X., Cao G.F., Cao X.X., Chang J.F., Chelkov G., Chen G., Chen H.S., Chen J.C., Chen L.P., Chen M.L., Chen P., Chen S.J., Chen Y.B., Chu Y.P., Cronin-Hennessy D., Dai H.L., Dai J.P., Dedovich D., Deng Z.Y., Denysenko I., Destefanis M., Ding Y., Dong L.Y., Dong M.Y., Du S.X., Duan M.Y., Fang J., Feng C.Q., Fu C.D., Fu J.L., Gao Y., Geng C., Goetzen K., Gong W.X., Greco M., Grishin S., Gu Y.T., Guo A.Q., Guo L.B., Guo Y.P., Han S.Q., Harris F.A., He K.L., He M., He Z.Y., Heng Y.K., Hou Z.L., Hu H.M., Hu J.F., Hu T., Hu X.W., Huang B., Huang G.M., Huang J.S., Huang X.T., Huang Y.P., Ji C.S., Ji Q., Ji X.B., Ji X.L., Jia L.K., Jiang L.L., Jiang X.S., Jiao J.B., Jin D.P., Jin S., Komamiya S., Kuehn W., Lange S., Leung J.K.C., Li C., Li C., Li D.M., Li F., Li G., Li H.B., Li J., Li J.C., Li L., Li L., Li Q.J., Li W.D., Li W.G., Li X.L., Li X.N., Li X.Q., Li X.R., Li Y.X., Li Z.B., Liang H., Liang T.R., Liang Y.T., Liang Y.F., Liao G.R., Liao X.T., Liu B., Liu C.L., Liu C.X., Liu C.Y., Liu F.H., Liu F., Liu F., Liu G.C., Liu H., Liu H.B., Liu H.M., Liu H.W., Liu J., Liu J.P., Liu K., Liu K.Y., Liu Q., Liu S.B., Liu X.H., Liu Y.B., Liu Y.F., Liu Y.W., Liu Y., Liu Z.A., Lu G.R., Lu J.G., Lu Q.W., Lu X.R., Lu Y.P., Luo C.L., Luo M.X., Luo T., Luo X.L., Ma C.L., Ma F.C., Ma H.L., Ma Q.M., Ma X., Ma X.Y., Maggiora M., Mao Y.J., Mao Z.P., Min J., Mo X.H., Muchnoi N.Y., Nefedov Y., Ning F.P., Olsen S.L., Ouyang Q., Pelizacus M., Peters K., Ping J.L., Ping R.G., Poling R., Pun J.C.S., Qi M., Qian S., Qiao C.F., Qiu J.F., Rong G., Ruan X.D., Sarantsev A., Shao M., Shen C.P., Shen X.Y., Sheng H.Y., Sonoda S., Spataro S., Spruck B., Sun D.H., Sun G.X., Sun J.F., Sun S.S., Sun X.D., Sun Y.J., Sun Y.Z., Sun Z.J., Sun Z.T., Tang C.J., Tang X., Tang X.F., Tian H.L., Toth D., Varner G.S., Wan X., Wang B.Q., Wang J.K., Wang K., Wang L.L., Wang L.S., Wang P., Wang P.L., Wang Q., Wang S.G., Wang X.D., Wang X.L., Wang Y.D., Wang Y.F., Wang Y.Q., Wang Z., Wang Z.G., Wang Z.Y., Wei D.H., Wen S.P., Wiedner U., Wu L.H., Wu N., Wu Y.M., Wu Z., Xiao Z.J., Xie Y.G., Xu G.F., Xu G.M., Xu H., Xu M., Xu M., Xu X.P., Xu Y., Xu Z.Z., Xue Z., Yan L., Yan W.B., Yan Y.H., Yang H.X., Yang M., Yang P., Yang S.M., Yang Y.X., Ye M., Ye M.H., Yu B.X., Yu C.X., Yu L., Yuan C.Z., Yuan Y., Zeng Y., Zhang B.X., Zhang B.Y., Zhang C.C., Zhang D.H., Zhang H.H., Zhang H.Y., Zhang J.W., Zhang J.Y., Zhang J.Z., Zhang L., Zhang S.H., Zhang X.Y., Zhang Y., Zhang Y.H., Zhang Z.P., Zhao C., Zhao H.S., Zhao J.W., Zhao J.W., Zhao L., Zhao L., Zhao M.G., Zhao Q., Zhao S.J., Zhao T.C., Zhao X.H., Zhao Y.B., Zhao Z.G., Zhemchugov A., Zheng B., Zheng J.P., Zheng Y.H., Zheng Z.P., Zhong B., Zhong J., Zhou L., Zhou Z.L., Zhu C., Zhu K., Zhu K.J., Zhu Q.M., Zhu X.W., Zhu Y.S., Zhu Z.A., Zhuang J., Zou B.S., Zou J.H., Zuo J.X. and Zweber P., Observation of a p(p)over-bar mass threshold enhancement in psi ' -> pi(+)pi(-)J/psi(J/psi -> gamma p(p)over-bar) decay, Chinese Physics C . Chinese Physical Soc, 2010, 34: 421-426. |
| Researcher : Qiao Z |
| List of Research Outputs |
| Qiao Z., Xing Y. and Wang J., Universal conductance fluctuation of mesoscopic systems in the metal-insulator crossover regime, Physical Review B. New York, The American Physical Society, 2010, 81: 085114: 1-6. |
| Researcher : Shan W |
| List of Research Outputs |
| Lu H., Shan W., Yao W., Niu Q. and Shen S.Q., Massive Dirac fermions and spin physics in an ultrathin film of topological insulator, Physical Review B. The American Physical Society, 2010, 81: 115407: 1-7. |
| Shan W., Lu H. and Shen S.Q., Effective continuous model for surface states and thin films of three-dimensional topological insulators, New Journal of Physics. Bristol, IOP Publishing Limited, 2010, 12: 043048: 1-23. |
| Researcher : Shen S |
| Project Title: | Spin transverse force and its applications in quantum spin and charge transport |
| Investigator(s): | Shen SQ |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2006 |
| Completion Date: | 08/2009 |
| Abstract: |
| (1) Purpose: The primary objective of this proposal is to investigate the motion of electron spins in an electric field and in electronic systems with strong spin-orbit coupling. This project will focus on the electron transport driven by the spin polarized current and spin current, and spin dependent effects such as the Aharonov-Casher effect and its relevance to spin transport. (2) Key issues: Spin-orbit coupling reflects the interaction of the electron spin, electron momentum and its environments. It is a potential route to control and to manipulate quantum spin state and coherent transport. As an extension of Ehrenfest’s theorem a quantum mechanical version of spin transverse force can be obtained in electronic systems with strong spin-orbit coupling. This force and the force balance in equilibrium states are very useful to investigate the spin transport effect. Based on the concept of spin force it will be anticipated to develop a theory for spin resolved charge quantum transport driven by spin polarized current and spin current, and anomalous charge transport in ferromagnetic metals and semiconductors, and to establish a relation between spin current and spin polarization. (3) Likely outcome: It is expected to develop a quantum transport theory based on the extended Ehrenfest’s theorem on spin force. The research results will be reported in the leading physics journals, such as Physical Review and Physics Review Letters. |
| Project Title: | Spin Transport in Interacting Quantum Dots |
| Investigator(s): | Shen SQ |
| Department: | Physics |
| Source(s) of Funding: | Small Project Funding |
| Start Date: | 09/2007 |
| Abstract: |
| The Kondo effect is of fundamental importance in a wide class of correlated electron systems, which involves the interaction between a localized spin and free conduction electrons, such as in metals containing magnetic impurities. About two decades ago, the Kondo effect was proposed to emerge in the device consisting of a single-electron quantum dot (QD) coupled to electrodes (i.e. leads), and its conductance can be strongly enhanced in the Kondo regime due to the frequent occurrence of higher-order co-tunneling process. Most early works focus on the Kondo physics driven by the charge current, which was generated in two non-magnetic leads and under the (charge) bias voltage V. Since electron has both charge and spin, it would be imcomplete for any physical picture of the Kondo effect without full consideration of quantum spin transport. Rapid progreees of the present nano-technology make it available to inject spin current in quantum dot, and to investigate the relevant transport properties. The objective of the present proposal is to establish a complete picture of Kondo resonance in the quantum dot in spin aspect as well as the charge aspect. |
| Project Title: | Theoretical Study of Optically Injected Spin Current and Its Scattering Effect |
| Investigator(s): | Shen SQ |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2007 |
| Abstract: |
| To explore the microscopic mechanism of the formation of spin current, spin polarization and photocurrent irradiated by the polarized light. To calculate the optically injected spin current, spin polarization and photocurrent quantitatively and to deduce these quantities from experimental measurements. To explore the relation between optical injection of spin current and spin photocurrent and band structure of semiconductors. To explore the electric effect caused by the spin current, and spin photocurrent, and possible measurement to distinguish physical mechanism of extrinsic and intrinsic spin Hall effect. |
| Project Title: | Topological phase transition and the Berry phase caused by spin-orbit coupling |
| Investigator(s): | Shen SQ |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2008 |
| Abstract: |
| 1) To explore the relation between quantum electron transport and the Berry phases of electrons in the momentum space in systems with spin-orbit coupling, sepcial attensions will be paid to the magnetoresistance, spin-polarized tarnsport, and phase diagram according to the topological phases of charge and spin carriers. 2) To explore the quantum transport in some mesoscopic systems such as mesocopic rings and/or quantum dots. It will focus on the topological transition and controllable manipulation of quantum states. |
| Project Title: | Controlling Quantum Spin and Magnetization by Spin Current |
| Investigator(s): | Shen SQ |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 10/2009 |
| Abstract: |
| To explore possible application of spin current and spin bias to manipulate and to detect noninvasively the quantum spin and magnetization in quantum dot, single molecular magnet or ferromagnetic grain or particles. Physical mechanism and dynamic procedure of magnetization reversal will be studied; to explore possible novel physical consequences induced by spin current |
| Project Title: | Quantum Order in Novel Materials: Superconductivity and Topological Order |
| Investigator(s): | Shen SQ, Ng TK, Wang ZD, Zhang FC |
| Department: | Physics |
| Source(s) of Funding: | Collaborative Research Fund (CRF) - Group Research Project |
| Start Date: | 06/2010 |
| Abstract: |
| (1) Understanding the physical properties of pnictide superconductors and topological insulators; in particular, the nature of quantum order in these materials and the associated experimental signatures; (2) Studying the phenomenology associated with the unusual properties of the materials, in particular the physical consequences of the proposed s state in pnictides superconductors and the unique topological edge excitations in topological insulators under different physical settings; and (3) Investigating the possible existence of general topologically ordered states and understanding the general mathematical structure behind quantum topological order and their implications in quantum information. |
| List of Research Outputs |
| Researcher : Shen SQ |
| Project Title: | Spin transverse force and its applications in quantum spin and charge transport |
| Investigator(s): | Shen SQ |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2006 |
| Completion Date: | 08/2009 |
| Abstract: |
| (1) Purpose: The primary objective of this proposal is to investigate the motion of electron spins in an electric field and in electronic systems with strong spin-orbit coupling. This project will focus on the electron transport driven by the spin polarized current and spin current, and spin dependent effects such as the Aharonov-Casher effect and its relevance to spin transport. (2) Key issues: Spin-orbit coupling reflects the interaction of the electron spin, electron momentum and its environments. It is a potential route to control and to manipulate quantum spin state and coherent transport. As an extension of Ehrenfest’s theorem a quantum mechanical version of spin transverse force can be obtained in electronic systems with strong spin-orbit coupling. This force and the force balance in equilibrium states are very useful to investigate the spin transport effect. Based on the concept of spin force it will be anticipated to develop a theory for spin resolved charge quantum transport driven by spin polarized current and spin current, and anomalous charge transport in ferromagnetic metals and semiconductors, and to establish a relation between spin current and spin polarization. (3) Likely outcome: It is expected to develop a quantum transport theory based on the extended Ehrenfest’s theorem on spin force. The research results will be reported in the leading physics journals, such as Physical Review and Physics Review Letters. |
| Project Title: | Spin Transport in Interacting Quantum Dots |
| Investigator(s): | Shen SQ |
| Department: | Physics |
| Source(s) of Funding: | Small Project Funding |
| Start Date: | 09/2007 |
| Abstract: |
| The Kondo effect is of fundamental importance in a wide class of correlated electron systems, which involves the interaction between a localized spin and free conduction electrons, such as in metals containing magnetic impurities. About two decades ago, the Kondo effect was proposed to emerge in the device consisting of a single-electron quantum dot (QD) coupled to electrodes (i.e. leads), and its conductance can be strongly enhanced in the Kondo regime due to the frequent occurrence of higher-order co-tunneling process. Most early works focus on the Kondo physics driven by the charge current, which was generated in two non-magnetic leads and under the (charge) bias voltage V. Since electron has both charge and spin, it would be imcomplete for any physical picture of the Kondo effect without full consideration of quantum spin transport. Rapid progreees of the present nano-technology make it available to inject spin current in quantum dot, and to investigate the relevant transport properties. The objective of the present proposal is to establish a complete picture of Kondo resonance in the quantum dot in spin aspect as well as the charge aspect. |
| Project Title: | Theoretical Study of Optically Injected Spin Current and Its Scattering Effect |
| Investigator(s): | Shen SQ |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2007 |
| Abstract: |
| To explore the microscopic mechanism of the formation of spin current, spin polarization and photocurrent irradiated by the polarized light. To calculate the optically injected spin current, spin polarization and photocurrent quantitatively and to deduce these quantities from experimental measurements. To explore the relation between optical injection of spin current and spin photocurrent and band structure of semiconductors. To explore the electric effect caused by the spin current, and spin photocurrent, and possible measurement to distinguish physical mechanism of extrinsic and intrinsic spin Hall effect. |
| Project Title: | Topological phase transition and the Berry phase caused by spin-orbit coupling |
| Investigator(s): | Shen SQ |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2008 |
| Abstract: |
| 1) To explore the relation between quantum electron transport and the Berry phases of electrons in the momentum space in systems with spin-orbit coupling, sepcial attensions will be paid to the magnetoresistance, spin-polarized tarnsport, and phase diagram according to the topological phases of charge and spin carriers. 2) To explore the quantum transport in some mesoscopic systems such as mesocopic rings and/or quantum dots. It will focus on the topological transition and controllable manipulation of quantum states. |
| Project Title: | Controlling Quantum Spin and Magnetization by Spin Current |
| Investigator(s): | Shen SQ |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 10/2009 |
| Abstract: |
| To explore possible application of spin current and spin bias to manipulate and to detect noninvasively the quantum spin and magnetization in quantum dot, single molecular magnet or ferromagnetic grain or particles. Physical mechanism and dynamic procedure of magnetization reversal will be studied; to explore possible novel physical consequences induced by spin current |
| Project Title: | Quantum Order in Novel Materials: Superconductivity and Topological Order |
| Investigator(s): | Shen SQ, Ng TK, Wang ZD, Zhang FC |
| Department: | Physics |
| Source(s) of Funding: | Collaborative Research Fund (CRF) - Group Research Project |
| Start Date: | 06/2010 |
| Abstract: |
| (1) Understanding the physical properties of pnictide superconductors and topological insulators; in particular, the nature of quantum order in these materials and the associated experimental signatures; (2) Studying the phenomenology associated with the unusual properties of the materials, in particular the physical consequences of the proposed s state in pnictides superconductors and the unique topological edge excitations in topological insulators under different physical settings; and (3) Investigating the possible existence of general topologically ordered states and understanding the general mathematical structure behind quantum topological order and their implications in quantum information. |
| List of Research Outputs |
| Chen J.C., Cheng S.G., Shen S.Q. and Sun Q.F., Electronic transport through a graphene-based ferromagnetic/normal/ferromagnetic junction, Journal of Physics-Condensed Matter. Bristol, IOP Publishing Limited, 2010, 22: 035301: 1-8. |
| Chu R., Li J., Jain J.K. and Shen S.Q., Coherent oscillations and giant edge magnetoresistance in singly connected topological insulators, Physical Review B (Rapid Communications). New York, The American Physical Society, 2009, 80: 081102: 1-4. |
| Dai J., Lu H., Yang C., Shen S.Q., Zhang F.C. and Cui X., Magnetoelectric photocurrent generated by direct interband transitions in InGaAs/InAlAs two-dimensional electron gas, Physical Review Letters. New York, The American Physical Society, 2010, 104: 246601: 1-4. |
| Jiang Z., Shen S.Q. and Zhang F.C., Disorder effect of resonant spin Hall effect in a tilted magnetic field, Physical Review B. New York, The American Physical Society, 2009, 80: 195301: 1-6. |
| Jiang Z., Chu R. and Shen S.Q., Electric-field modulation of the number of helical edge states in thin-film semiconductors, Physical Review B. New York, The American Physical Society, 2010, 81: 115322: 1-4. |
| Li P. and Shen S.Q., Fermionic representation of a symmetrically frustrated SU(3) model: Application to the Haldane-gap antiferromagnets, Physics Letters A. Amsterdam, Elsevier B.V., 2009, 373: 3075-3078. |
| Lu H. and Shen S.Q., Detecting and switching magnetization of Stoner nanograin in nonlocal spin valve, Physical Review B. New York, The American Physical Society, 2009, 80: 094401: 1-15. |
| Lu H., Shan W., Yao W., Niu Q. and Shen S.Q., Massive Dirac fermions and spin physics in an ultrathin film of topological insulator, Physical Review B. The American Physical Society, 2010, 81: 115407: 1-7. |
| Shan W., Lu H. and Shen S.Q., Effective continuous model for surface states and thin films of three-dimensional topological insulators, New Journal of Physics. Bristol, IOP Publishing Limited, 2010, 12: 043048: 1-23. |
| Shen S.Q., Croucher Senior Research Fellowship, 2010. |
| Wen W., Shen S.Q. and Huang G., Propagation of sound and supersonic bright solitons in superfluid Fermi gases in BCS-BEC crossover, Physical Review B. New York, The American Physical Society, 2010, 81: 014528: 1-11. |
| Researcher : So CW |
| List of Research Outputs |
| So C.W., Observational studies of the night sky in Hong Kong. Hong Kong, The University of Hong Kong, 2010, 1-147. |
| Researcher : Takata J |
| List of Research Outputs |
| Takata J., Wang Y. and Cheng K.S., Pulsar high energy emissions from outer gap accelerator closed by a magnetic pair-creation process, The Astrophysical Journal. The American Astronomical Society, 2010, 715: 1318-1326. |
| Trepl L., Hui C.Y., Cheng K.S., Takata J., Wang Y., Liu Z.Y. and Wang N., Multiwavelength properties of a new Geminga-like pulsar: PSR J2021+4026, Monthly Notices of the Royal Astronomical Society. United Kingdom, Royal Astronomical Society, 2010, 405: 1339-1348. |
| Researcher : Tian X |
| List of Research Outputs |
| Cheng K.S., Harko T.C., Huang Y.F., Lin L.M., Suen W.M. and Tian X., Relativistic mass ejecta from phase-transition-induced collapse of neutron stars, Journal of Cosmology and Astroparticle Physics. Bristol, IOP Publishing Limited, 2009, 007: 1-30. |
| Researcher : To CK |
| List of Research Outputs |
| Fan J., Zhu C., Fung S.H.Y., Zhong Y.C., Wong K.S., Xie Z., Brauer G., Anwand W., Skorupa W., To C.K., Yang B., Beling C.D. and Ling F.C.C., Arsenic doped p-type zinc oxide films grown by radio frequency magnetron sputtering, Journal of Applied Physics. New York, American Institute of Physics, 2009, 106: 073709: 1-6. |
| Researcher : Tong DSY |
| Project Title: | ICMAT 2001 International Conference on Materials for Advanced Technologies Initial Stage Growth of GaN on SiC(0001) and its Implication to Defect Formation in the Film |
| Investigator(s): | Tong DSY |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 07/2001 |
| Abstract: |
| N/A |
| Researcher : Tong WY |
| List of Research Outputs |
| Tong W.Y., Chen H.Y., Djurisic A., Ng A.M.C., Wang H., Gwo S. and Chan W.K., Infrared photoluminescence from α- and β-copper phthalocyanine nanostructures, Optical Materials. Amsterdam, Elsevier B.V., 2010, 32: 924-927. |
| Researcher : Tung S |
| List of Research Outputs |
| Tung S., Radon potential mapping in Hong Kong. Hong Kong, The University of Hong Kong, 2010, 1-147. |
| Researcher : Wang B |
| List of Research Outputs |
| Wang B., Ab-initio calculation of quantum AC transport in nanoscale structures. Hong Kong, The University of Hong Kong, 2009, 1-127. |
| Wang B., Chu R., Wang J. and Guo H., First-principles calculation of chiral current and quantum self-inductance of carbon nanotubes, Physical Review B. New York, The American Physical Society, 2009, 80: 235430: 1-5. |
| Wang B. and Wang J., First-principles investigation of transport properties through longitudinal unzipped carbon nanotubes, Physical Review B. New York, The American Physical Society, 2010, 81: 045425: 1-6. |
| Wang B., Xing Y., Zhang L. and Wang J., Transient dynamics of molecular devices under a steplike pulse bias, Physical Review B (Rapid Communications). New York, The American Physical Society, 2010, 81: 121103: 1-4. |
| Researcher : Wang B |
| List of Research Outputs |
| Wang B., Ab-initio calculation of quantum AC transport in nanoscale structures. Hong Kong, The University of Hong Kong, 2009, 1-127. |
| Wang B., Chu R., Wang J. and Guo H., First-principles calculation of chiral current and quantum self-inductance of carbon nanotubes, Physical Review B. New York, The American Physical Society, 2009, 80: 235430: 1-5. |
| Wang B. and Wang J., First-principles investigation of transport properties through longitudinal unzipped carbon nanotubes, Physical Review B. New York, The American Physical Society, 2010, 81: 045425: 1-6. |
| Wang B., Xing Y., Zhang L. and Wang J., Transient dynamics of molecular devices under a steplike pulse bias, Physical Review B (Rapid Communications). New York, The American Physical Society, 2010, 81: 121103: 1-4. |
| Researcher : Wang H |
| List of Research Outputs |
| Tong W.Y., Chen H.Y., Djurisic A., Ng A.M.C., Wang H., Gwo S. and Chan W.K., Infrared photoluminescence from α- and β-copper phthalocyanine nanostructures, Optical Materials. Amsterdam, Elsevier B.V., 2010, 32: 924-927. |
| Researcher : Wang J |
| Project Title: | Quantum spin transport through nano-devices in the presence of spin-spin interaction |
| Investigator(s): | Wang J |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2006 |
| Completion Date: | 08/2009 |
| Abstract: |
| (1) Recently, considerable interest has been paid to the quantum physics of spin-current. It is believed that a controlled spin-current generation, detection, and usage can provide interesting applications to spintronics. Spin-current generation has been classified as "extrinsic" or "intrinsic". An extrinsic spin-current is generated by external physical factors and driving forces of the spintronics device, such as optical spin injection achieved experimentally and the various spin pumps studied theoretically. An intrinsic spin-current is generated by physical factors existed inside the spintronic device, notable is that generated by various spin-orbit interactions. In particular, it has been theoretically predicted that non-magnetic systems with spin-orbit interaction and under an external electric field, can generate a spin-current flowing perpendicular to the electric field. Such an spin-current is termed "dissipation-less" because the electron motion is perpendicular to the electric field. (2) There are so far extensive theoretical work on spin-current physics, and some experimental works have also appeared which may provide support to some of the theories. Despite the increasing literature on spin-current physics, it is recognized that the definition of spin-current itself is still somewhat controversial. If one mimics the definition of charge-current, then a spin-current can be defined as the quantum average of the time derivative of spin density. In its simplest form at steady state, such a definition gives a spin-current that is equal to the particle current with spin-up subtracted by the particle current with spin-down multiplied by the spin of the electron. Clearly, this is a very intuitive definition of spin-current and is adopted by most of the work in literature. (3) Since both spin and velocity are vectors, the spin-current is a tensor. In systems where there is a spin-orbit interaction, the spin density is not conserved: spins can rotate from their initial orientation due to the interaction. Therefore, spin-current becomes a non-conservative quantity. A quantity which is not conserved is difficulty to study experimentally and indeed, it is unclear what is even measured if an experimental detection method can be found to measure spin-current. Without knowing what is measured, the definition of spin-current becomes non-unique and there have been several definitions in literature. Although it is unclear a priori if a measurable spin-current must be conserved, the property of conservation would be nice to have, at least theoretically. (4) In this project, we will investigate this problem by using the conventional definition of spin-current, but we will include a spin-spin interaction (bascally it is similar to the dipole-dipole interaction) into the Hamiltonian for computing the quantum average. Our preliminary result shows that the spin current obtained in such an analysis is conserved because the spin-spin interaction will generate a new term in the spin current which cancels the non-conserved spin current. Since dipole interactions between spins are possible, including their contribution and consequence of spin-current conservation in such a self-consistent analysis is rather natural. (5) In addition, the conserved spin-current gives a linear spin-conductance, we will develop a phenomenological theory for this spin-conductance for multi-probe device systems so that the spin-conductance is a conserved quantity. In this approach, we will enforce two conditions on the spin current: (1). the spin current must be conserved and (2). the spin current is caused by the external bias and hence depends only on the difference between external bias. With these two conditions, the non-conserved spin current can be partitioned into each electrode similar to the approach of Buttiker in treating ac charge transport. (6) Finally, with this new defintion of spin current developed and new spin-spin interaction introduced, the study of various spin transport properties can be carried on. For instance, we can examine the spin accumulation for a two-terminal device and spin Hall current for a four-terminal device with or without disorder as well as external magnetic field. |
| Project Title: | The spin-Hall conductance fluctuation in the presence of Rashba interaction |
| Investigator(s): | Wang J |
| Department: | Physics |
| Source(s) of Funding: | Small Project Funding |
| Start Date: | 09/2007 |
| Abstract: |
| The notion of dissipation-less spin-current
has attracted considerable interests recently. In its
simplest form, a spin-current is about the flow of
spin-up electrons in one direction, say +x, accompanied
by the flow of equal number of spin-down electrons
in the opposite direction, -x. The total charge current
in the x-direction is therefore zero and the total
spin-current is finite. For a pure semiconductor system
with spin-orbital (SO) interactions, it has been shown
that an electric field in the z-direction can induce
the flow of a spin-current in the x-direction perpendicular
to the electric field: such a spin-current is dissipation-less
because the external electric
field does no work to
the electrons flowing inside the spin-current. If the
semiconductor sample has a finite x-extent, the flow
of spin-current should cause a spin accumulation at
the edges of the sample, resulting to a situation that
spin-up electrons accumulate at one edge while spin-down
electrons at the opposite edge. Hence a spin-Hall effect
is produced where chemical potentials for the two spin
channels become different at the two edges of the sample.
This interesting phenomenon has been subjected to extensive
studies and there are several experiments reporting
spin accumulation which may have provided evidence
of this effect. It has been shown that for a pure two
dimensional (2d) sample without any impurities, the
Rashba SO interaction generates a spin-Hall conductivity
having universal value. It has also been shown that
any presence of weak disorder destroies this spin-Hall
effect
in the large sample limit. On the other hand,
numerical studies have provided evidence that for mesoscopic
samples, spin-Hall conductance can survive weak disorder.
One
of the most striking quantum transport features in
mesoscopic regime is the universal charge conductance
fluctuation
(UCF)\cite{web1,althu,lee85}: quantum
interference gives rise to the sample-to-sample fluctuation
of charge conductance of order e*e/h, independent of
the details of the disorder, Fermi energy, and the
sample size as long as transport is in the coherent
diffusive regime characterized by the relation between
relevant length scales, l |
| Project Title: | The spin-Hall "phase diagram" and spin-Hall conductance fluctuation at low magnetic field in the mesoscopic regime |
| Investigator(s): | Wang J |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 01/2008 |
| Abstract: |
| The situation becomes very interesting and more complicated when a perpendicular uniform external magnetic field is applied to the 2D sample. In this case, and become functions of . Most importantly, a magnetic field can produce edge-states which are responsible for the integer quantum Hall effect (IQHE). Similar to the well known studies of the global phase diagram of quantum Hall effect[9], it will be very useful to map out the low field “phase diagram" of MSHE in terms of the field strength and the disorder strength . Such a diagram allows one to clearly understand the role played by the edge-states and disorder. It is the purpose of this proposal to present this MSHE “phase diagram" for four-probe 2D disordered mesoscopic samples with linear Rashba and/or Dresselhaus SO interactions. Here we put “phase diagram" in quotes because the physics we study is mesoscopic, namely for samples in the coherent diffusive regime characterized by the relation between relevant length scales, . Here is the linear sample size, the elastic mean free path and the phase coherence length. As such, the “phases" in the “phase diagram" are states with zero or finite values of and , and no phase transitions are implied between these states. In this project, we will determine numerically the “phase diagram" of MSHE in terms of magnetic field , disorder strength , and SO interaction strength . We expect a rich “phase diagram" due to the edge state, and the competition between SO interaction that randomizes the spin direction and the Zeeman energy that favors spin polarization along a fixed direction. We will study the spin-Hall conductance fluctuations in the presence of magnetic field in various “phases". Experimentally it is difficult to directly measure the spin current, the electric means to indirectly detect the spin current would be useful. In this proposal, we will study the voltage fluctuation induced by the fluctuation of spin-Hall current using H-shaped structures. Finally, we wish to address the issue of shot noise of spin-Hall current and the correction of the voltage induced by the correction of the spin-Hall current. |
| Project Title: | Quantum inductance and capacitance in nano-devices at finite frequencies |
| Investigator(s): | Wang J |
| Department: | Physics |
| Source(s) of Funding: | Small Project Funding |
| Start Date: | 09/2008 |
| Abstract: |
| For a very small conductor in which quantum effects play a role, it is not difficult to imagine that capacitance of the conductor may behave differently from the familiar classical case. For a small conductor its discrete nature of electron energy levels can be important, and the quantum correction due to the finite density of states (DOS) of the plates is known as the quantum capacitance. For a microscopic sized conductor in which quantum coherence is maintained, one must consider the role played by the leads which connect the conductor to the outside world. One also needs to consider the finite screening length of the interacting electrons when it is not small compared with the system size. At these very small length scales, the relevant capacitance is the electrochemical capacitance C , which is a quantity depending on the electronic properties of the conductor. Capacitance plays a central role in many phenomena such as the Coulomb blockade, and it is very important for several experimental techniques. However, there have been no quantitative predictions of capacitance for microscopic systems. Thus, we do not yet know its dependence on the atomic valence orbitals, the environment (e.g., the leads), and the shape, size, and other properties of a nanosystem. The purpose of this project is to make this connection by theoretically investigating capacitance of atomic junctions. In particular we shall study junctions formed by a small cluster of atoms where the clusters are sandwiched in between two metallic leads. We emphasize small system size where quantum effects are dominant and we answer a number of very relevant questions: (i) What is the value of the capacitance of these atomic junctions? (ii) What is the effect of atomic orbitals? (iii) How do we characterize the behavior of the capacitance? (iv) For the tip-substrate system familiar to scanning tunneling microscopy (STM), what is the C as function of distance? (v) Finally, what is the nature of quantum inductance? Although atomic nanosystems are of great current interest, these fundamental questions, which are important to ac transport, have not been addressed. It is clear that capacitance, inductance, and many other mechanical and electrical properties of atomic junctions can be obtained only from detailed first principle analysis. This will be our approach. In this project, we will first develop a theory for generalized frequency dependent capacitance that includes the information of quantum inductance and then apply our theory to nano-devices. |
| Project Title: | The nature of edge states in the integer quantum Hall regime |
| Investigator(s): | Wang J |
| Department: | Physics |
| Source(s) of Funding: | Small Project Funding |
| Start Date: | 01/2009 |
| Abstract: |
| When a two-dimensional mesoscopic sample is subjected to external magnetic field, peculiar electronic states --- edge states, may be established at the boundaries of the sample. Classically, Lorentz force pushes electrons toward the sample boundary and electron trajectories become skipping orbits. Edge states can be considered as the quantum version of skipping orbits. Importantly, edge states in mesoscopic samples provide necessary density of states (DOS) between the Landau levels, integer quantum Hall effect (IQHE) can therefore occur in the clean sample limit. In contrast, for infinitely large samples, a degree of disorder in the sample appears necessary which provides DOS in between Landau levels to stablize the Fermi energy for IQHE. Nevertheless, increasing disorder will eventually destroy IQHE and how does this happen has been an important issue attracting numerous studies. Here we address the disorder issue for mesoscopic samples, namely how edge states are destroyed by disorder in the IQHE regime and, at a fixed filling factor larger than one, are edge states destroyed all at once or one by one. These important questions provide insight to the IQHE phase diagram for mesoscopic samples, and may shed light to similar problems in samples of infinite size. In this project, we shall address these questions by extensive calculations on a mesoscopic graphene system and a square lattice model to map out a ``phase diagram" of edge states in the presence of disorder. Here the ``phases" in the ``phase diagram" denote quantum states and no phase transitions are implied between these states. We will use transmission eigen-channels to characterize edge states. |
| Project Title: | The first principle study of local heating and heat transport in nano-devices |
| Investigator(s): | Wang J |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 01/2009 |
| Abstract: |
| 1) On the theoretical side, the present electronic heat transport theory does not take the Coulomb interaction into account. As a result, the electronic heat current does not obey the gauge invariant, i.e., the heat current must only depend on the voltage difference. Clearly there is a need for a density functional theory (DFT) based transport theory that can deal with heat transport as well the heat dissipation. 2) In this project, we will develop a new local heat dissipation theory based on non-equilibrium Green’s function method that is combined with the first principle DFT method. We will modify the definition of conventional current density so that the current obtained from the current density gives the correct result. 3) We will formulate an ac heat transport theory using non-equilibrium Green’s function method. In particular, we will include the self-consistent Coulomb interaction into account to make sure that the heat current depends only on the voltage difference. |
| Project Title: | Outstanding Researcher Award 2008-2009 |
| Investigator(s): | Wang J |
| Department: | Physics |
| Source(s) of Funding: | Outstanding Researcher Award |
| Start Date: | 12/2009 |
| Abstract: |
| The Awards are intended to recognize, reward, and promote exceptional research accomplishments of academic and research staff. |
| Project Title: | Quantum transport in nanostructures |
| Investigator(s): | Wang J |
| Department: | Physics |
| Source(s) of Funding: | Croucher Senior Research Fellowships in Natural Sciences, Technology and Medicine |
| Start Date: | 12/2009 |
| Abstract: |
| Refer to hard copy |
| Project Title: | Theoretical investigation of dynamic response, fluctuations, and charge relaxations in disordered mesoscopic conductors. |
| Investigator(s): | Wang J |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 01/2010 |
| Abstract: |
| 1) In this project, we will formulate a general frequency dependent nonlinear transport theory that is current conserving and gauge invariant based the non-equilibrium Green's function approach. The key issue is that the internal Coulomb potential and the induced vector potential generated by the time dependent voltage must be considered self-consistently. The reason one has to consider the induced vector potential is due to the Ampere-Maxwell's law and Faraday's law. 2) In this project, we will also study frequency dependent shot noise, the frequency dependent electro-chemical capacitance, as well as the charge relaxation and the charge fluctuations in mesoscopic or nanoscopic disordered conductors. 3) Through this study, we hope to achieve two goals: (1). Establishing current conserving and gauge invariant formalisms for these transport properties. (2). Investigating numerical these quantities in the diffusive regime and studying universal features. 4) Finally, we will study the charge relaxation resistance in the presence of superconducting lead. |
| List of Research Outputs |
| Cheng S.G., Xing Y., Wang J. and Sun Q.F., Controllable Andreev retroreflection and specular Andreev reflection in a four-terminal graphene-superconductor hybrid system, Physical Review Letters. New York, The American Physical Society, 2009, 103: 167003: 1-4. |
| Qiao Z., Xing Y. and Wang J., Universal conductance fluctuation of mesoscopic systems in the metal-insulator crossover regime, Physical Review B. New York, The American Physical Society, 2010, 81: 085114: 1-6. |
| Wang B., Chu R., Wang J. and Guo H., First-principles calculation of chiral current and quantum self-inductance of carbon nanotubes, Physical Review B. New York, The American Physical Society, 2009, 80: 235430: 1-5. |
| Wang B. and Wang J., First-principles investigation of transport properties through longitudinal unzipped carbon nanotubes, Physical Review B. New York, The American Physical Society, 2010, 81: 045425: 1-6. |
| Wang B., Xing Y., Zhang L. and Wang J., Transient dynamics of molecular devices under a steplike pulse bias, Physical Review B (Rapid Communications). New York, The American Physical Society, 2010, 81: 121103: 1-4. |
| Wang J., Outstanding researcher award, 2008-2009 , the University of Hong Kong. 2010. |
| Wang J., Gao J. and Wang L., Resistance steps and asymmetric conduction induced by currents in La0.8Ca0.2MnO3 films, IEEE Transactions on Magnetics. IEEE, 2010, 46: 1-8. |
| Xing Y., Wang J. and Sun Q.F., Focusing of electron flow in a bipolar graphene ribbon with different chiralities, Physical Review B. New York, The American Physical Society, 2010, 81: 165425: 1-10. |
| Xing Y., Sun Q.F. and Wang J., Nernst and Seebeck effects in a graphene nanoribbon, Physical Review B. New York, The American Physical Society, 2009, 80: 235411: 1-8. |
| Researcher : Wang J |
| List of Research Outputs |
| Cheng S.G., Xing Y., Wang J. and Sun Q.F., Controllable Andreev retroreflection and specular Andreev reflection in a four-terminal graphene-superconductor hybrid system, Physical Review Letters. New York, The American Physical Society, 2009, 103: 167003: 1-4. |
| Qiao Z., Xing Y. and Wang J., Universal conductance fluctuation of mesoscopic systems in the metal-insulator crossover regime, Physical Review B. New York, The American Physical Society, 2010, 81: 085114: 1-6. |
| Wang B., Chu R., Wang J. and Guo H., First-principles calculation of chiral current and quantum self-inductance of carbon nanotubes, Physical Review B. New York, The American Physical Society, 2009, 80: 235430: 1-5. |
| Wang B. and Wang J., First-principles investigation of transport properties through longitudinal unzipped carbon nanotubes, Physical Review B. New York, The American Physical Society, 2010, 81: 045425: 1-6. |
| Wang B., Xing Y., Zhang L. and Wang J., Transient dynamics of molecular devices under a steplike pulse bias, Physical Review B (Rapid Communications). New York, The American Physical Society, 2010, 81: 121103: 1-4. |
| Wang J., Outstanding researcher award, 2008-2009 , the University of Hong Kong. 2010. |
| Wang J., Gao J. and Wang L., Resistance steps and asymmetric conduction induced by currents in La0.8Ca0.2MnO3 films, IEEE Transactions on Magnetics. IEEE, 2010, 46: 1-8. |
| Xing Y., Wang J. and Sun Q.F., Focusing of electron flow in a bipolar graphene ribbon with different chiralities, Physical Review B. New York, The American Physical Society, 2010, 81: 165425: 1-10. |
| Xing Y., Sun Q.F. and Wang J., Nernst and Seebeck effects in a graphene nanoribbon, Physical Review B. New York, The American Physical Society, 2009, 80: 235411: 1-8. |
| Researcher : Wang L |
| List of Research Outputs |
| Wang J., Gao J. and Wang L., Resistance steps and asymmetric conduction induced by currents in La0.8Ca0.2MnO3 films, IEEE Transactions on Magnetics. IEEE, 2010, 46: 1-8. |
| Wang Z., Yu G.L., Qiu L., Wu X.S., Wang L. and Gao J., Magnetically tunable properties related with carriers density in self-doped La1−xMnO3/y wt %Nb-SrTiO3 heteroepitaxial junctions, Journal of Applied Physics. New York, American Institute of Physics, 2010, 107: 09C704: 1-3. |
| Researcher : Wang Y |
| List of Research Outputs |
| Takata J., Wang Y. and Cheng K.S., Pulsar high energy emissions from outer gap accelerator closed by a magnetic pair-creation process, The Astrophysical Journal. The American Astronomical Society, 2010, 715: 1318-1326. |
| Trepl L., Hui C.Y., Cheng K.S., Takata J., Wang Y., Liu Z.Y. and Wang N., Multiwavelength properties of a new Geminga-like pulsar: PSR J2021+4026, Monthly Notices of the Royal Astronomical Society. United Kingdom, Royal Astronomical Society, 2010, 405: 1339-1348. |
| Researcher : Wang Z |
| Project Title: | International Conference on Magnetism Magnetic, Charge, and Orbital Orderings in Manganites |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 08/2000 |
| Abstract: |
| N/A |
| Project Title: | Annual American Physical Society March Meeting 2002 Nonadiabatic Geometric Phase Shift in Quantum Computation using Superconducting Nanocircuits |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 03/2002 |
| Abstract: |
| N/A |
| Project Title: | Quantum logic gates based on cyclic geometric phases |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | Small Project Funding |
| Start Date: | 11/2002 |
| Abstract: |
| To design a set of quantum logic gates in quantum computing operations with fast running speed based on cyclic geometric phases, which may provide a method to overcome the intrinsic difficulty in adiabatic geometric operations associated with the slow gate speed. |
| Project Title: | The Fourth International Conference on New Theories, Discoveries and Applications of Superconductors and Related Materials Impurity State of D-wave Superconductors |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 01/2003 |
| Abstract: |
| N/A |
| Project Title: | Vortex state and impurity effect in newly discovered NaCoO superconductors |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | Small Project Funding |
| Start Date: | 11/2003 |
| Abstract: |
| To study theoretically vortex state and impurity effect in the novel superconductors with triangular lattices. |
| Project Title: | Interdisciplinary cutting edge research related to condensed matter physics: solid state quantum computing and quantum information processing |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | Matching Fund for NSFC Young Researcher Award |
| Start Date: | 03/2005 |
| Abstract: |
| To study interdisciplinary cutting edge research related to condensed matter physics: solid state quantum computing and quantum information processing. |
| Project Title: | Fault-tolerant quantum computing |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | Croucher Senior Research Fellowships in Natural Sciences, Technology and Medicine |
| Start Date: | 09/2007 |
| Abstract: |
| Refer to hard copy |
| Project Title: | Exploring new geometric quantum computaion schemes |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 10/2007 |
| Abstract: |
| Combining our earlier idea of non-adiabatic geometric quantum gates with the adiabatic non-Abelian (holonomic) geometric computing, we intend to develop for the first time a more efficient but simple adiabatic Abelian geometric quantum computation scheme. This scenario, apart from its global geometric feature that is robust against operational errors, is expected to possess both the advantages of two existing geometric schemes: being easy in the gate design/operation due to the adiabatic condition and having more available qubit systems because of the Abelian (non-degenerate two levels) nature. We plan to elaborate how to implement this new scheme in physical systems like superconducting circuits and NMR-type systems. In the frame work of our recent theory for the geometric phase of invariant operators, we attempt to design a universal set of quantum gates based on geometric phase shifts of the invariant operators’ eigenstates. Since an invariant operator has three unique properties: (i) all eigenvalues are time-independent; (ii) the evolving state of its initial eigenstate is always its eigenstate at any time; (iii) no transition occurs among different eigen-levels, such geometric gates may be more insensitive not only to local operational errors but also to environmental noises. Physical implementation will also be addressed. By the integration of the geometric phase scenario and a key idea of the decoherence-free coding (DFC), we plan to propose a new kind of geometric quantum computation strategy with decoherence-free codes. Since the DFC is usually immune to certain environmental noises while the geometric quantum computation is resilient to operational errors, our new strategy is expected to be more robust against the errors and has a great potential to increase the fidelity of quantum gates to a higher level. We will work out several experimentally feasible schemes and try to collaborate with experimentalists. |
| Project Title: | Theoretical exploration of topological phases and their applications in quantum information processing |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 10/2008 |
| Abstract: |
| 1) We attempt to explore various topological phases/orders and to identify topological quantum phase transitions based on various quantum entanglement scenarios as well as to examine the stability/robustness of topological phases against various perturbations. Besides, we also plan to simulate numerically some distinct features of topological order or fractional statistics in condensed matter systems, such as the half-quantum vortex state in chiral p-wave superconductors subject to strong magnetic field, and to address how to detect these feature experimentally. 2) We plan to design theoretically several implementable Hamiltonians having topological phases with superconducting qubits in the cavity and ultracold atoms in optical lattices. Moreover, we intend to address their potential and promising applications for quantum information processing. |
| Project Title: | Theoretical Exploration of Newly Discovered FeAs Superconductors |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 01/2009 |
| Abstract: |
| A very recent discovery of superconductivity in the new family of layered FeAs compounds with higher transition temperatures has stimulated significant experimental and theoretical interest on these new superconductors, including physical properties with a distinct multi-band feature. Although a number of preliminary efforts have been devoted to understand the origin of superconductivity and magnetic fluctuations in the systems, more in-depth and relevant theoretical studies are desirably waited, particularly on how the multi-band feature play a key/important role on various physical properties with or without inhomogeneity. In this project, we attempt to study theoretically several interesting, important and timely issues in this emerging field. (i) We propose to first study magnetic/superconducting orders and fluctuations by more reliable theoretical approaches (like self-consistent RPA/FLEX) based on the two/three-band models in homogenous systems to account for some existing experimental results as well as to suggest new experiments to test some predictions. (ii) We plan to explore impurity states in the antiferromagnetic spin-density wave and superconducting states of the iron arsenide based on a simplified two/three model. The impurity-induced variations of the local density of states will be examined, which can be detected by the scanning tunneling microscopy (STM), as done in high-Tc cuprates. (iii) We attempt to study the local electronic structure at vortex cores by self-consistently solving the BdG equations modeled for these systems. Fruitful vortex states will be revealed, which can also be tested by the STM. |
| Project Title: | Theoretical Studies of FeAs Superconductors |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2009 |
| Abstract: |
| To first study magnetic/superconducting orders and fluctuations by more reliable theoretical approaches (like self-consistent RPA/FLEX) based on the two/three-band models in homogenous systems, with emphasis on the doping and model parameter dependence, to account for some existing experimental results as well as to suggest new experiments to test some predictions; to explore impurity states in the antiferromagnetic spin-density wave and superconducting states of the iron arsenide based on a simplified two/three model; to study the local electronic structure at vortex cores by self-consistently solving the BdG equations modeled for these systems subject to a magnetic field; to investigate the various tunneling properties of superconducting junctions, including the Josephson effect and Andreev reflection, with one side or both as the FeAs systems modeled by a multi-band model |
| Project Title: | Exploring novel properties of relativistic particles with cold atoms |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 02/2010 |
| Abstract: |
| The recent progress in the field of ultracold atoms has stimulated intensive efforts to explore and to simulate various exotic and complex quantum phenomena. A number of model Hamiltonians that are important in condensed matters have been realized effectively by cold atoms. Notably, several intriguing properties of Dirac particles was predicted a long time ago, but the direct experimental observations seems still awaited. In this project, we aim to the following objectives. (1) We attempt to design an experimental feasible scheme to realize one-dimensional relativistic quantum systems with controllable parameters. We will then study theoretically the abnormal quantum transmission across a given potential barrier, which has been known as the famous Klein tunneling, predicted to have a very intriguing tunneling feature different from that of usual non- relativistic quantum tunneling observed in condensed matter systems. In addition, we plan also to explore theoretically the effects of interactions on the relativistic quantum transport. (2) We intend to design a two (or three)-dimensional relativistic quantum system with ultracold atoms subject to the appropriate laser beams and to look into the relativistic quantum transport. In particular, we will study the geometric phase accumulated in the Dirac particle’s motion for both adiabatic and non-adiabatic cases and present our predictions to be verified by future experiments with ultracold atoms. |
| Project Title: | Quantum Order in Novel Materials: Superconductivity and Topological Order |
| Investigator(s): | Wang ZD, Ng TK, Shen SQ, Zhang FC |
| Department: | Physics |
| Source(s) of Funding: | Collaborative Research Fund (CRF) - Group Research Project |
| Start Date: | 06/2010 |
| Abstract: |
| (1) Understanding the physical properties of pnictide superconductors and topological insulators; in particular, the nature of quantum order in these materials and the associated experimental signatures; (2) Studying the phenomenology associated with the unusual properties of the materials, in particular the physical consequences of the proposed s state in pnictides superconductors and the unique topological edge excitations in topological insulators under different physical settings; and (3) Investigating the possible existence of general topologically ordered states and understanding the general mathematical structure behind quantum topological order and their implications in quantum information. |
| List of Research Outputs |
| Wang Z., Yu G.L., Qiu L., Wu X.S., Wang L. and Gao J., Magnetically tunable properties related with carriers density in self-doped La1−xMnO3/y wt %Nb-SrTiO3 heteroepitaxial junctions, Journal of Applied Physics. New York, American Institute of Physics, 2010, 107: 09C704: 1-3. |
| Researcher : Wang Z |
| List of Research Outputs |
| Wang Z., Yu G.L., Qiu L., Wu X.S., Wang L. and Gao J., Magnetically tunable properties related with carriers density in self-doped La1−xMnO3/y wt %Nb-SrTiO3 heteroepitaxial junctions, Journal of Applied Physics. New York, American Institute of Physics, 2010, 107: 09C704: 1-3. |
| Researcher : Wang ZD |
| Project Title: | International Conference on Magnetism Magnetic, Charge, and Orbital Orderings in Manganites |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 08/2000 |
| Abstract: |
| N/A |
| Project Title: | Annual American Physical Society March Meeting 2002 Nonadiabatic Geometric Phase Shift in Quantum Computation using Superconducting Nanocircuits |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 03/2002 |
| Abstract: |
| N/A |
| Project Title: | Quantum logic gates based on cyclic geometric phases |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | Small Project Funding |
| Start Date: | 11/2002 |
| Abstract: |
| To design a set of quantum logic gates in quantum computing operations with fast running speed based on cyclic geometric phases, which may provide a method to overcome the intrinsic difficulty in adiabatic geometric operations associated with the slow gate speed. |
| Project Title: | The Fourth International Conference on New Theories, Discoveries and Applications of Superconductors and Related Materials Impurity State of D-wave Superconductors |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 01/2003 |
| Abstract: |
| N/A |
| Project Title: | Vortex state and impurity effect in newly discovered NaCoO superconductors |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | Small Project Funding |
| Start Date: | 11/2003 |
| Abstract: |
| To study theoretically vortex state and impurity effect in the novel superconductors with triangular lattices. |
| Project Title: | Interdisciplinary cutting edge research related to condensed matter physics: solid state quantum computing and quantum information processing |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | Matching Fund for NSFC Young Researcher Award |
| Start Date: | 03/2005 |
| Abstract: |
| To study interdisciplinary cutting edge research related to condensed matter physics: solid state quantum computing and quantum information processing. |
| Project Title: | Fault-tolerant quantum computing |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | Croucher Senior Research Fellowships in Natural Sciences, Technology and Medicine |
| Start Date: | 09/2007 |
| Abstract: |
| Refer to hard copy |
| Project Title: | Exploring new geometric quantum computaion schemes |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 10/2007 |
| Abstract: |
| Combining our earlier idea of non-adiabatic geometric quantum gates with the adiabatic non-Abelian (holonomic) geometric computing, we intend to develop for the first time a more efficient but simple adiabatic Abelian geometric quantum computation scheme. This scenario, apart from its global geometric feature that is robust against operational errors, is expected to possess both the advantages of two existing geometric schemes: being easy in the gate design/operation due to the adiabatic condition and having more available qubit systems because of the Abelian (non-degenerate two levels) nature. We plan to elaborate how to implement this new scheme in physical systems like superconducting circuits and NMR-type systems. In the frame work of our recent theory for the geometric phase of invariant operators, we attempt to design a universal set of quantum gates based on geometric phase shifts of the invariant operators’ eigenstates. Since an invariant operator has three unique properties: (i) all eigenvalues are time-independent; (ii) the evolving state of its initial eigenstate is always its eigenstate at any time; (iii) no transition occurs among different eigen-levels, such geometric gates may be more insensitive not only to local operational errors but also to environmental noises. Physical implementation will also be addressed. By the integration of the geometric phase scenario and a key idea of the decoherence-free coding (DFC), we plan to propose a new kind of geometric quantum computation strategy with decoherence-free codes. Since the DFC is usually immune to certain environmental noises while the geometric quantum computation is resilient to operational errors, our new strategy is expected to be more robust against the errors and has a great potential to increase the fidelity of quantum gates to a higher level. We will work out several experimentally feasible schemes and try to collaborate with experimentalists. |
| Project Title: | Theoretical exploration of topological phases and their applications in quantum information processing |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 10/2008 |
| Abstract: |
| 1) We attempt to explore various topological phases/orders and to identify topological quantum phase transitions based on various quantum entanglement scenarios as well as to examine the stability/robustness of topological phases against various perturbations. Besides, we also plan to simulate numerically some distinct features of topological order or fractional statistics in condensed matter systems, such as the half-quantum vortex state in chiral p-wave superconductors subject to strong magnetic field, and to address how to detect these feature experimentally. 2) We plan to design theoretically several implementable Hamiltonians having topological phases with superconducting qubits in the cavity and ultracold atoms in optical lattices. Moreover, we intend to address their potential and promising applications for quantum information processing. |
| Project Title: | Theoretical Exploration of Newly Discovered FeAs Superconductors |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 01/2009 |
| Abstract: |
| A very recent discovery of superconductivity in the new family of layered FeAs compounds with higher transition temperatures has stimulated significant experimental and theoretical interest on these new superconductors, including physical properties with a distinct multi-band feature. Although a number of preliminary efforts have been devoted to understand the origin of superconductivity and magnetic fluctuations in the systems, more in-depth and relevant theoretical studies are desirably waited, particularly on how the multi-band feature play a key/important role on various physical properties with or without inhomogeneity. In this project, we attempt to study theoretically several interesting, important and timely issues in this emerging field. (i) We propose to first study magnetic/superconducting orders and fluctuations by more reliable theoretical approaches (like self-consistent RPA/FLEX) based on the two/three-band models in homogenous systems to account for some existing experimental results as well as to suggest new experiments to test some predictions. (ii) We plan to explore impurity states in the antiferromagnetic spin-density wave and superconducting states of the iron arsenide based on a simplified two/three model. The impurity-induced variations of the local density of states will be examined, which can be detected by the scanning tunneling microscopy (STM), as done in high-Tc cuprates. (iii) We attempt to study the local electronic structure at vortex cores by self-consistently solving the BdG equations modeled for these systems. Fruitful vortex states will be revealed, which can also be tested by the STM. |
| Project Title: | Theoretical Studies of FeAs Superconductors |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2009 |
| Abstract: |
| To first study magnetic/superconducting orders and fluctuations by more reliable theoretical approaches (like self-consistent RPA/FLEX) based on the two/three-band models in homogenous systems, with emphasis on the doping and model parameter dependence, to account for some existing experimental results as well as to suggest new experiments to test some predictions; to explore impurity states in the antiferromagnetic spin-density wave and superconducting states of the iron arsenide based on a simplified two/three model; to study the local electronic structure at vortex cores by self-consistently solving the BdG equations modeled for these systems subject to a magnetic field; to investigate the various tunneling properties of superconducting junctions, including the Josephson effect and Andreev reflection, with one side or both as the FeAs systems modeled by a multi-band model |
| Project Title: | Exploring novel properties of relativistic particles with cold atoms |
| Investigator(s): | Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 02/2010 |
| Abstract: |
| The recent progress in the field of ultracold atoms has stimulated intensive efforts to explore and to simulate various exotic and complex quantum phenomena. A number of model Hamiltonians that are important in condensed matters have been realized effectively by cold atoms. Notably, several intriguing properties of Dirac particles was predicted a long time ago, but the direct experimental observations seems still awaited. In this project, we aim to the following objectives. (1) We attempt to design an experimental feasible scheme to realize one-dimensional relativistic quantum systems with controllable parameters. We will then study theoretically the abnormal quantum transmission across a given potential barrier, which has been known as the famous Klein tunneling, predicted to have a very intriguing tunneling feature different from that of usual non- relativistic quantum tunneling observed in condensed matter systems. In addition, we plan also to explore theoretically the effects of interactions on the relativistic quantum transport. (2) We intend to design a two (or three)-dimensional relativistic quantum system with ultracold atoms subject to the appropriate laser beams and to look into the relativistic quantum transport. In particular, we will study the geometric phase accumulated in the Dirac particle’s motion for both adiabatic and non-adiabatic cases and present our predictions to be verified by future experiments with ultracold atoms. |
| Project Title: | Quantum Order in Novel Materials: Superconductivity and Topological Order |
| Investigator(s): | Wang ZD, Ng TK, Shen SQ, Zhang FC |
| Department: | Physics |
| Source(s) of Funding: | Collaborative Research Fund (CRF) - Group Research Project |
| Start Date: | 06/2010 |
| Abstract: |
| (1) Understanding the physical properties of pnictide superconductors and topological insulators; in particular, the nature of quantum order in these materials and the associated experimental signatures; (2) Studying the phenomenology associated with the unusual properties of the materials, in particular the physical consequences of the proposed s state in pnictides superconductors and the unique topological edge excitations in topological insulators under different physical settings; and (3) Investigating the possible existence of general topologically ordered states and understanding the general mathematical structure behind quantum topological order and their implications in quantum information. |
| List of Research Outputs |
| Bai Y., Ye M. and Wang Z.D., Entanglement monogamy and entanglement evolution in multipartite systems, Physical Review A (Brief Reports). New York, The American Physical Society, 2009, 80: 044301: 1-4. |
| He G. and Wang Z.D., Single qubit quantum secret sharing with improved security, Quantum Information & Computation. Rinton Press, Inc, 2010, 10: 28-40. |
| Jiang H., Li J.X. and Wang Z.D., Vortex states in iron-based superconductors with collinear antiferromagnetic cores, Physical Review B. New York, The American Physical Society, 2009, 80: 134505: 1-8. |
| Li Y., Zhang P. and Wang Z.D., Extended JC-Dicke model for two-component atomic BEC inside a cavity, European Physical Journal D. Springer, 2010, 58: 379-384. |
| Wang Z.D., Delocalization of relativistic Dirac particles in disordered one-dimensional systems, The 8th International Conference on Condensed Matters Theory and Computational Materials Science. 2009. |
| Wang Z.D., Exotic orbital-transverse density-wave instabilities in multi-orbital systems (Invited talk), Workshop on Theoretical Physics, 5-6 June 2010, Guangzhou. 2010. |
| Wang Z.D., Exotic orbital-transverse density-wave orders in quantum systems(Plenary Talk), Workshop on Quantum Engineering and Physics of Quantum Coherence Device, 18-24 June 2010, Guangzhou. 2010. |
| Wang Z.D., Topological quantum computing with superconducting devices, The International Conference on Quantum Foundation and Technology: Frontier and Future . 2009. |
| Wang Z.D., Vortex states in iron-based superconductors (Invited Talk), The 2009 International Workshop on Frontiers of Theoretical and Computational Physics and Chemistry, Shouzhou. 2009. |
| Xue Z., Zhu S. and Wang Z.D., Quantum computation in a decoherence-free subspace with superconducting devices, European Physical Journal D. EDP Sciences, 2009, 55: 223-228. |
| Ye F., Chen Y., Wang Z.D. and Zhang F.C., Imbalanced superfluid state in an annular disk, Journal of Physics: Condensed Matter. Bristol, IOP Publishing Limited, 2009, 21: 355701: 1-8. |
| Ye M., Bai Y.K., Lin X.M. and Wang Z.D., Exploration of nonlocalities in ensembles consisting of bipartite quantum states, Physical Review A (Brief Reports). New York, The American Physical Society, 2010, 81: 014303: 1-4. |
| Researcher : Wen Y |
| List of Research Outputs |
| Wen Y., Theoretical and experimental studies of electronic states in InAs/GaAs self-assembled quantum dots. Hong Kong, The University of Hong Kong, 2009, 1-62. |
| Researcher : Wong KC |
| List of Research Outputs |
| Wong K.C., Inflation and late time acceleration of the universe by variable brane tension in braneworld model. Hong Kong, The University of Hong Kong, 2009, 1-81. |
| Wong K.C., Cheng K.S. and Harko T.C., Inflation and late-time acceleration in braneworld cosmological models with varying brane tension, European Physical Journal C. Springer, 2010, 68: 241-253. |
| Researcher : Wong YL |
| List of Research Outputs |
| Kong S., Wong Y.L., Huang Y.F. and Cheng K.S., Variation of microphysics in wind bubbles: An alternative mechanism for explaining the rebrightenings in Gamma-ray burst afterglows, Monthly Notices of the Royal Astronomical Society. United Kingdom, Royal Astronomical Society, 2010, 402: 409-416. |
| Researcher : Wu HS |
| Project Title: | Surface atomic structure extraction from low energy electron diffraction patterson function |
| Investigator(s): | Wu HS |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 09/2004 |
| Abstract: |
| A new method named structure extraction from LEED PF is fully implementing by correctly addressing the two issues; (1) a complex system often has PF spots overlap or missing, which makes structure extraction much harder; (2) real systems often have two domains or even more domains in the surface structure, which also makes structure extraction more complicated. |
| Project Title: | 13th International Conference on Surface Science Accurate & Fast Calculation of Low Energy Electron Diffraction Spectra with Full Crystal Potential |
| Investigator(s): | Wu HS |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 07/2007 |
| Abstract: |
| N/A |
| Project Title: | Accurate & fast calculation of low energy electron diffraction spectra with full crystal potential |
| Investigator(s): | Wu HS |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2007 |
| Abstract: |
| To further improve the important FD program for even more accurate and smooth calculation. To significantly reduce both storage memory and computing time by implementing into this program a new method, the slab combing method, that has just been developed by the PI and has had significant result on both 1-D and 2-D samples. To use this program to carry out calculations of LEED spectra of some reconstructed semiconductor surfaces that MS theory usually had relatively large R-factors, such as SiC(0001) 3x3. Ordered nanostructures, such as C60 on cupper substrate, will also be calculated. |
| Project Title: | Studies of Fundamental Properties of Nanosurfaces and Selected Applications |
| Investigator(s): | Wu HS, Djurisic A |
| Department: | Physics |
| Source(s) of Funding: | Collaborative Research Fund (CRF) - Group Research Project |
| Start Date: | 06/2009 |
| Abstract: |
| The performance of nanoscale devices is often dominated by their surface properties. For example, surfaces introduce undesired electronic states in electronic and optoelectronic devices constructed from semiconducting nanostructures. By contrast, surface activity should be enhanced in nanostructures used as antibacterial agents. To improve such performance, our aim is to provide quantitative atomic-scale information about nanoscale surfaces. Our project will achieve this by introducing a new methodology; we will intentionally design and fabricate novel and highly-controlled nanoplatforms that allow for the first time detailed determination of surface structure and modeling of their relevant surface properties. |
| Researcher : Xi Y |
| List of Research Outputs |
| Brauer G., Anwand W., Grambole D., Egger W., Sperr P., Beinik I., Wang L., Teichert C., Kuriplach J., Lang J., Zviagin S., Cizmar E., Ling F.C.C., Hsu Y.F., Xi Y., Chen X., Djurisic A. and Skorupa W., Characterization of ZnO nanostructures: A challenge to positron annihilation spectroscopy and other methods, physica status solidi (c). Weinheim, Wiley-VCH Verlag GmbH & Co., 2009, 6: 2556-2560. |
| Ng M.C.A., Xi Y., Hsu Y.F., Djurisic A., Chan W.K., Gwo S., Tam H.L., Cheah K.W., Fong P.W.K., Lui H.F. and Surya C., GaN/ZnO nanorod light emitting diodes with different emission spectra, Nanotechnology. Bristol, IOP Publishing Limited, 2009, 20: 445201: 1-8. |
| Xi Y., Huang B., Djurisic A., Chan M.N., Leung F.C.C., Chan W.K. and Au D.T.W., Electrodeposition for antibacterial nickel-oxide-based coatings, Thin Solid Films. Amsterdam, Elsevier B.V., 2009, 517: 6527-6530. |
| Researcher : Xie MH |
| Project Title: | Growth and properties of AlInN thin films |
| Investigator(s): | Xie MH |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2006 |
| Completion Date: | 02/2010 |
| Abstract: |
| (1) There exists a large miscibility gap in AlInN alloy and so it is difficult to grow AlInN with arbitrary alloy composition. In this project, the incorporation kinetics of the constituent Al and In elements will be studied. Equipped with such a knowledge, alloys with wide composition ranges will be explored. (2) AlInN grown on GaN represents a unique heteroepitaxial system where the strain can be tuned between compressive and tensile states by changing the alloy composition. Here, an investigation of heteroepitaxial growth mode and the strain effect will be carried out. (3) Finally, characterizations of AlInN epilayers will be conducted for their structural and other physical properties. |
| Project Title: | Magnetic nanostructures on GaN 一 the quantum confinement and interface effects |
| Investigator(s): | Xie MH |
| Department: | Physics |
| Source(s) of Funding: | NSFC/RGC Joint Research Scheme |
| Start Date: | 01/2008 |
| Abstract: |
| (1) To fabricate magnetic nanoparticles or atomically flat thin films with precisely controlled size (thickness) and shape on GaN by MBE. Explore the effects of surface and interfacial parameters on growth dynamics. (2) To investigate microstructure and magnetic properties of the nanostructures. Establish the correlation among the growth. The structure and the magnetic properties of the nanostructures. (3) To predict/explain the novel magnetic properties of the nanostructures/thin films by theoretical and computational studies. Suggest the directions of future research in this important area. |
| Project Title: | Epitaxial InGaN on Si: n-InGaN/ p-Si hetero-junction for potential photovoltaic applications |
| Investigator(s): | Xie MH |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2008 |
| Abstract: |
| 1) Study of epitaxial growth mode of InGaN on Si: Due to the lattice mismatch and chemical dissimilarity of InGaN and Si, the epitaxial growth of InGaN on Si could be complex and difficult. So, this project will firstly probe the growth behavior of InGaN, including the growth mode and surface morphology. 2) Study of interface of InGaN and Si: Interface strain and defects will be studied by techniques such as TEM, XRD and STM. Different substrate surfaces and growth strategies will be explored for better materials. 3) Characterization for electrical/opticval properties: the properties of the Si/InGaN heterojunctions will be characterized, and the potential of the material in photovoltaic application will be evaluated. |
| Project Title: | SemiconNano 2009 Heteroepitaxial InN on GaN(0001): Interface, Strain, and Island Formation |
| Investigator(s): | Xie MH |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 08/2009 |
| Completion Date: | 08/2009 |
| Abstract: |
| N/A |
| Project Title: | Growth and doping of ultrathin layers of Bi2Se3, a topological insulator, by molecular-beam epitaxy |
| Investigator(s): | Xie MH |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 01/2010 |
| Abstract: |
| The objective of this research is to successfully grow and dope ultrathin layers of Bi2Se3, a compound belonging to the new class of materials, the topological insulator (TI), for their novel transport properties. Specifically, the following issues will be addressed in this proposal: 1. Identifying suitable substrates and optimizating the MBE condition for ultrathin films of Bi2Se3 growth: The TI materials were discovered only recently, which have since drawn a lot of attention in physics community, as they hold great promises for applications in future information technology. One of such materials is Bi2Se3, a narrow bandgap semiconductor. Up to now, the reported experimental work on this material system have been on crystals of the bulk forms, usually grown by some thermal methods. However, bulk crystals have some limitations associated with high background doping and the difficulty in accessing the size effect. Therefore, in this proposal, I shall attempt to grow ultrathin layers of Bi2Se3 using the technique of Molecular-Beam Epitaxy (MBE), which is known to offer superior controls over layer thickness and doping. To successfully grow high quality Bi2Se3 thin films by MBE, the first issue of concern is to identify a suitable substrate over which epitaxial growth proceeds layer-by-layer. One common substrate is silicon (Si), where its (111) surface provides a suitable template for Bi2Se3 epitaxial growth due to their similar atomic structural symmetry. However, considering the large lattice mismatch between Si and Bi2Se3, it may not be the best candidate. Therefore, other substrate materials, such as GaAs and InP, will also be experimented for their suitability as the substrates. Having identified a suitable substrate, the MBE conditions need to be optimized for high quality epitaxial thin films in terms of crystallinity and background doping. To this end, different flux combinations between Bi and Se sources and the temperatures of deposition will be mapped out. In order to investigate the size dependence of the TI states, layers of varying thickness ranging from one to several atomic units will also be fabricated. 2. Doping of magnetic and non-magnetic impurities: Doping of Bi2Se3 by magnetic and non-magnetic impurities is an important aspect of TI research. According to theory, non-magnetic impurity would not disturb the surface states due to the topological protection by the time-reversal symmetry. On the other hand, magnetic impurity effects the time-reversal symmetry and alters the surface transport characteristics of the material. I shall thus introduce dopants of different types into Bi2Se3 during MBE. Examples of such dopants include Co for magnetic doping and Au for non-magnetic doping. Surface electron transport characteristics will then be compared by, e.g., low-temperature scanninfg tunneling spectroscopy and angle-resolved photoelectron spectroscopy measurements. Such a study can be expected to lead to new discoveries of novel phenomena and new physics, thus contribute to this emerging field of condensed matter research. |
| List of Research Outputs |
| Djurisic A., Xie M.H. and Leung Y.H., Doping of wide band gap nanostructures: ZnO and GaN, In: W. Chen, Doped Nanomaterials and Nanodevices. American Scientific Publishers, 2010, Chapter 4: 101-133. |
| Li H., Zhong G.H., Lin H.Q. and Xie M.H., Reactive interface formation and Co-induced (√7×√7) superstructure on a GaN(0001) pseudo-(1×1) substrate surface, Physical Review B (Brief Reports). New York, The American Physical Society, 2010, 81: 233302: 1-4. |
| Li H., He K., Xie M.H., Wang N., Jia J.F. and Xue Q.K., Surface modification for epitaxial growth of single crystalline cobalt thin films with uniaxial magnetic anisotropy on GaN(0001)-1×1 surfaces, New Journal of Physics. Bristol, IOP Publishing Limited, 2010, 12: 073007: 1-9. |
| Zhong G.H., Li Y.L., Yan P., Liu Z., Xie M.H. and Lin H.Q., Structural, electronic, and electrochemical properties of cathode materials Li2MSiO4 (M = Mn, Fe, and Co): Density functional calculations, Journal of Physical Chemistry C. American Chemical Society, 2010, 114: 3693-3700. |
| Researcher : Xing Y |
| List of Research Outputs |
| Cheng S.G., Xing Y., Wang J. and Sun Q.F., Controllable Andreev retroreflection and specular Andreev reflection in a four-terminal graphene-superconductor hybrid system, Physical Review Letters. New York, The American Physical Society, 2009, 103: 167003: 1-4. |
| Qiao Z., Xing Y. and Wang J., Universal conductance fluctuation of mesoscopic systems in the metal-insulator crossover regime, Physical Review B. New York, The American Physical Society, 2010, 81: 085114: 1-6. |
| Wang B., Xing Y., Zhang L. and Wang J., Transient dynamics of molecular devices under a steplike pulse bias, Physical Review B (Rapid Communications). New York, The American Physical Society, 2010, 81: 121103: 1-4. |
| Xing Y., Wang J. and Sun Q.F., Focusing of electron flow in a bipolar graphene ribbon with different chiralities, Physical Review B. New York, The American Physical Society, 2010, 81: 165425: 1-10. |
| Xing Y., Sun Q.F. and Wang J., Nernst and Seebeck effects in a graphene nanoribbon, Physical Review B. New York, The American Physical Society, 2009, 80: 235411: 1-8. |
| Researcher : Xu S |
| Project Title: | Multi-photon-excited photoluminescence and dynamic processes of photogenerated carriers in high-quality zinc oxide bulk crystals and nanostructures |
| Investigator(s): | Xu SJ, Zhao Y |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2006 |
| Completion Date: | 12/2009 |
| Abstract: |
| Thanks to ZnO's large exciton binding energy and potential applications in optoelectronic devices, considerable interest has risen recently on stimulated emission in ZnO thin films and nanostructures at room temperature. Exploitation of optoelectronic applications of ZnO requires a good understanding of various optical processes in ZnO thin films and nanostructures including ultrafast carrier dynamics. At present, very little is known about the multi-photon-absorption-induced luminescence and related issues such as carrier dynamics and the role of exciton-phonon interactions in ZnO. The proposed project aims at understanding mechanisms underlying multi-photon-excited photoluminescence in high-quality ZnO bulk crystals and nanostructures. Following outcomes are to be anticipated from the proposed studies: (1) Enhanced understanding of up-conversion photoluminescence in wide-gap polar semiconductors and related nanostructures. Determination of characteristic decay times of various luminescence lines of ZnO under excitations of intense femtosecond near-infrared laser employing accurate time-resolved PL techniques. Improved knowledge on exciton-phonon interactions and their role in the luminescence processes in polar semiconductors with strong exciton-phonon coupling. Elucidating the role of deep centers in multi-photon excited luminescence processes in wide-gap semiconductors. (2) ZnO in its bulk and nanostructure forms has recently demonstrated great potentials in applications in novel exciton-type optoelectronic devices. As a consequence, up-conversion luminescence in ZnO induced by multi-photon absorption is of particular interest and significance. Detailed investigations of up-conversion luminescence and carrier dynamics in ZnO employing state-of-the-art laser spectroscopic techniques will provide a wealth of knowledge both on fundamental physics and for design and fabrication of innovative optoelectronic devices. We have previously reported what is believed to be the first. (3) observation of intense up-conversion luminescence in bulk ZnO at room temperature in Optics Letters. Building up on the exciting preliminary work, the proposed studies here will expand and deepen our knowledge base in semiconductor photophysics in general and up-conversion photoluminescence of ZnO in particular. Research efforts as proposed here not only help keep Hong Kong at the cutting edge of technological innovations that produce novel optoelectronic devices, but also benefit the Territory by training local graduate students and establishing scientific collaborations with leading experts globally. All these will enhance the international competitive profile of Hong Kong in the scientific arena. |
| Project Title: | Investigation of ultrafast spin dynamics of photoexcited carriers in ultrafine InAs/GaAs layered quantum structures |
| Investigator(s): | Xu SJ |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 10/2008 |
| Abstract: |
| 1) Demonstration of selective excitation of the conduction electrons with opposite spin orientations in the InAs/GaAs layered quantum structures by means of polarized light. 2) Investigation of the initial spin relaxation of the charge carriers within 10 picosecond times in the InAs/GaAs layered quantum structures employing precise time-resolved Kerr rotation technique. 3) Elucidating the effect of correlated electron-hole pairs such as excitons in the initial spin dynamics of the photoexcited carriers in the InAs/GaAs layered quantum structures. |
| Project Title: | Luminescence blinking behavior and imaging of individual In-rich nano-dots in InGaN/GaN quantum wells |
| Investigator(s): | Xu SJ |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 01/2009 |
| Abstract: |
| InGaN/GaN quantum wells (QWs) are the technologically important strtcures for fabrication of short-wavelength light emitting devices including laser diodes. Due to the unavoidable phase separation effect, nano-sized In-rich clusters or dots can spontaneously form during the growth of InGaN/GaN quantum wells. Such nano-sized In-rich nanoclusters play a very important role in the luminescence process in InGaN/GaN QWs. In the proposed study, luminescence spectra and images of individual InGaN nano-clusters inside GaN matrix will be investigated by using confocal micro-luminescence technique. Blinking behavior of light emissions from individual InGaN dots as well as their "on"-"off" dynamics will be addressed. |
| Project Title: | Raman scattering spectra and imagings of self-assembled Si nanocrystals grown on SiC substrates |
| Investigator(s): | Xu SJ |
| Department: | Physics |
| Source(s) of Funding: | Small Project Funding |
| Start Date: | 01/2010 |
| Abstract: |
| After well established as the leading microelectronic material for many years, nonlinear optical properties, such as, stimulated Raman light scattering and /or Raman light lasing of silicon (Si) have recently attracted a great deal of interest. In particular, the first demonstration of continuous-wave Raman lasing in silicon in 2005 represents a significant milestone work in Si-based photonics and optoelectronics. However, how to reduce the lasing threshold power of the Si-based Raman lasers is still a very challenging task. Besides the optimization of device structure design such as cavity mirror and length design, a significant enhancement of the Raman light scattering efficiency in designed medium (Si) perhaps represents a correct direction towards the solution of the problem. At least, it can definitely promote the optical gain of the Si medium. Therefore, searching for Si novel microstructures having improved Raman light emitting efficiency becomes extremely desirable. Very recently, it has been found that one kind of Si nanocrystals (NCs) composite structures can be self-assembly formed when we did GaN thin film growth on Si-rich SiC surfaces by using molecular beam epitaxy (MBE). More interestingly, such Si NCs composites have been preliminarily shown to have one important property of Raman light scattering enhancement. One main objective of this proposed study is to conduct a detailed Raman light scattering characterization on the Si NCs composites self-assembly formed on the Si-rich SiC surfaces during the MBE growth of thin GaN layer. Based on the existing preliminary results and available experimental facilities, following issues are justified to be addressed: 1. Simultaneous observation of Raman scattering spectra and images of single Si NCs composite structures by using confocal scanning Raman microscopy/spectroscopy. 2. Structure characterization of the same individual Si NCs composite structures with high-resolution scanning electron microscopy. |
| List of Research Outputs |
| Researcher : Xu SJ |
| Project Title: | Multi-photon-excited photoluminescence and dynamic processes of photogenerated carriers in high-quality zinc oxide bulk crystals and nanostructures |
| Investigator(s): | Xu SJ, Zhao Y |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2006 |
| Completion Date: | 12/2009 |
| Abstract: |
| Thanks to ZnO's large exciton binding energy and potential applications in optoelectronic devices, considerable interest has risen recently on stimulated emission in ZnO thin films and nanostructures at room temperature. Exploitation of optoelectronic applications of ZnO requires a good understanding of various optical processes in ZnO thin films and nanostructures including ultrafast carrier dynamics. At present, very little is known about the multi-photon-absorption-induced luminescence and related issues such as carrier dynamics and the role of exciton-phonon interactions in ZnO. The proposed project aims at understanding mechanisms underlying multi-photon-excited photoluminescence in high-quality ZnO bulk crystals and nanostructures. Following outcomes are to be anticipated from the proposed studies: (1) Enhanced understanding of up-conversion photoluminescence in wide-gap polar semiconductors and related nanostructures. Determination of characteristic decay times of various luminescence lines of ZnO under excitations of intense femtosecond near-infrared laser employing accurate time-resolved PL techniques. Improved knowledge on exciton-phonon interactions and their role in the luminescence processes in polar semiconductors with strong exciton-phonon coupling. Elucidating the role of deep centers in multi-photon excited luminescence processes in wide-gap semiconductors. (2) ZnO in its bulk and nanostructure forms has recently demonstrated great potentials in applications in novel exciton-type optoelectronic devices. As a consequence, up-conversion luminescence in ZnO induced by multi-photon absorption is of particular interest and significance. Detailed investigations of up-conversion luminescence and carrier dynamics in ZnO employing state-of-the-art laser spectroscopic techniques will provide a wealth of knowledge both on fundamental physics and for design and fabrication of innovative optoelectronic devices. We have previously reported what is believed to be the first. (3) observation of intense up-conversion luminescence in bulk ZnO at room temperature in Optics Letters. Building up on the exciting preliminary work, the proposed studies here will expand and deepen our knowledge base in semiconductor photophysics in general and up-conversion photoluminescence of ZnO in particular. Research efforts as proposed here not only help keep Hong Kong at the cutting edge of technological innovations that produce novel optoelectronic devices, but also benefit the Territory by training local graduate students and establishing scientific collaborations with leading experts globally. All these will enhance the international competitive profile of Hong Kong in the scientific arena. |
| Project Title: | Investigation of ultrafast spin dynamics of photoexcited carriers in ultrafine InAs/GaAs layered quantum structures |
| Investigator(s): | Xu SJ |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 10/2008 |
| Abstract: |
| 1) Demonstration of selective excitation of the conduction electrons with opposite spin orientations in the InAs/GaAs layered quantum structures by means of polarized light. 2) Investigation of the initial spin relaxation of the charge carriers within 10 picosecond times in the InAs/GaAs layered quantum structures employing precise time-resolved Kerr rotation technique. 3) Elucidating the effect of correlated electron-hole pairs such as excitons in the initial spin dynamics of the photoexcited carriers in the InAs/GaAs layered quantum structures. |
| Project Title: | Luminescence blinking behavior and imaging of individual In-rich nano-dots in InGaN/GaN quantum wells |
| Investigator(s): | Xu SJ |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 01/2009 |
| Abstract: |
| InGaN/GaN quantum wells (QWs) are the technologically important strtcures for fabrication of short-wavelength light emitting devices including laser diodes. Due to the unavoidable phase separation effect, nano-sized In-rich clusters or dots can spontaneously form during the growth of InGaN/GaN quantum wells. Such nano-sized In-rich nanoclusters play a very important role in the luminescence process in InGaN/GaN QWs. In the proposed study, luminescence spectra and images of individual InGaN nano-clusters inside GaN matrix will be investigated by using confocal micro-luminescence technique. Blinking behavior of light emissions from individual InGaN dots as well as their "on"-"off" dynamics will be addressed. |
| Project Title: | Raman scattering spectra and imagings of self-assembled Si nanocrystals grown on SiC substrates |
| Investigator(s): | Xu SJ |
| Department: | Physics |
| Source(s) of Funding: | Small Project Funding |
| Start Date: | 01/2010 |
| Abstract: |
| After well established as the leading microelectronic material for many years, nonlinear optical properties, such as, stimulated Raman light scattering and /or Raman light lasing of silicon (Si) have recently attracted a great deal of interest. In particular, the first demonstration of continuous-wave Raman lasing in silicon in 2005 represents a significant milestone work in Si-based photonics and optoelectronics. However, how to reduce the lasing threshold power of the Si-based Raman lasers is still a very challenging task. Besides the optimization of device structure design such as cavity mirror and length design, a significant enhancement of the Raman light scattering efficiency in designed medium (Si) perhaps represents a correct direction towards the solution of the problem. At least, it can definitely promote the optical gain of the Si medium. Therefore, searching for Si novel microstructures having improved Raman light emitting efficiency becomes extremely desirable. Very recently, it has been found that one kind of Si nanocrystals (NCs) composite structures can be self-assembly formed when we did GaN thin film growth on Si-rich SiC surfaces by using molecular beam epitaxy (MBE). More interestingly, such Si NCs composites have been preliminarily shown to have one important property of Raman light scattering enhancement. One main objective of this proposed study is to conduct a detailed Raman light scattering characterization on the Si NCs composites self-assembly formed on the Si-rich SiC surfaces during the MBE growth of thin GaN layer. Based on the existing preliminary results and available experimental facilities, following issues are justified to be addressed: 1. Simultaneous observation of Raman scattering spectra and images of single Si NCs composite structures by using confocal scanning Raman microscopy/spectroscopy. 2. Structure characterization of the same individual Si NCs composite structures with high-resolution scanning electron microscopy. |
| List of Research Outputs |
| Xu S.J., Controlled Optical Injections and Initial Coherent Dynamics of Electron Spins in Semiconductor Quantum Disks, 6th Asian Conference on Ultrafast Phenomena. 2010. |
| Xu S.J., Who is who in the world, 2009, Marquis, USA . 2009. |
| Researcher : Xue Z |
| List of Research Outputs |
| Xue Z., Implementation of fault-tolerant quantum computation with superconducting device. Hong Kong, The University of Hong Kong, 2009, 1-100. |
| Xue Z., Zhu S. and Wang Z.D., Quantum computation in a decoherence-free subspace with superconducting devices, European Physical Journal D. EDP Sciences, 2009, 55: 223-228. |
| Researcher : Yang B |
| List of Research Outputs |
| Fan J., Zhu C., Fung S.H.Y., Zhong Y.C., Wong K.S., Xie Z., Brauer G., Anwand W., Skorupa W., To C.K., Yang B., Beling C.D. and Ling F.C.C., Arsenic doped p-type zinc oxide films grown by radio frequency magnetron sputtering, Journal of Applied Physics. New York, American Institute of Physics, 2009, 106: 073709: 1-6. |
| Researcher : Yang C |
| List of Research Outputs |
| Dai J., Lu H., Yang C., Shen S.Q., Zhang F.C. and Cui X., Magnetoelectric photocurrent generated by direct interband transitions in InGaAs/InAlAs two-dimensional electron gas, Physical Review Letters. New York, The American Physical Society, 2010, 104: 246601: 1-4. |
| Yang C., Dai J., Ge W.K. and Cui X., Determination of the sign of g factors for conduction electrons using time-resolved Kerr rotation, Applied Physics Letters. New York, American Institute of Physics, 2010, 96: 152109: 1-3. |
| Researcher : Yang K |
| List of Research Outputs |
| Chen W., Yang K., Zhou Y. and Zhang F.C., Theory for superconductivity in iron pnictides at large Coulomb U limit, Frontiers of Physics in China. Higher Education Press, 2009, 4: 447-454. |
| Researcher : Yao W |
| Project Title: | The study of spin and orbital dynamics in graphene and carbon nanotube |
| Investigator(s): | Yao W |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 04/2009 |
| Abstract: |
| The objective is to theoretically investigate the possibility to control spin and orbital dynamics in graphene and carbon nanotube, and the possibility of using the spin and orbital degrees of freedom for non-volatile information processing in these carbon-based materials. The study to be supported by the seed fund will establish preliminary results so as to strengthen the proposal to be submitted for RGC fund. |
| Project Title: | Optical preparation of nuclear spin bath for enhancing single electron spin coherence time in a quantum dot |
| Investigator(s): | Yao W |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 09/2009 |
| Abstract: |
| 1) Investigate the possible actions on the nuclear spin bath when the electronic states in a semiconductor quantum dot is excited and manipulated by optical fields. Find a unified treatment of the coupled interplay between the nuclear spin bath, the electronic states, and the optical fields. 2) Investigate the hyperfine interaction between the nuclear spin and the heavy-hole constitution of the charged exciton state in the relevant quantum dot geometries and experimental setups. Understand the possible actions on nuclear spin baths from hole spin, and explore the potential of this new ingredient on nuclear spin control. 3) Explore control schemes that can prepare the nuclear spin bath from the initial thermal distribution into a non-thermal distribution with narrowed inhomogeneous broadening, for enhancing the electron spin coherence time in semiconductor quantum dot. |
| List of Research Outputs |
| Lu H., Shan W., Yao W., Niu Q. and Shen S.Q., Massive Dirac fermions and spin physics in an ultrathin film of topological insulator, Physical Review B. The American Physical Society, 2010, 81: 115407: 1-7. |
| Yao W., Optical and electrical controls of nuclear state preparation for suppressing electron spin decoherence in a quantum dot, The 6th Joint Meeting of the Chinese Physicists Worldwide - International Conference on Physics Education and Frontier Physics. 2009. |
| Yao W., Preparation of nuclear spin environment for an electron spin qubit, Workshop on Quantum Engineering and Physics of Quantum Coherence Device. 2010. |
| Yao W., Valley dependent physics in graphene, Program on Progress in Spintronics and Graphene Research, Kavli Institute for Theoretical Physics China. 2010. |
| Yao W., Valley dependent physics in graphene, The 2nd Guangdong‐Hong Kong Joint Workshop on Physics. 2009. |
| Researcher : Ye F |
| List of Research Outputs |
| Ye F., Chen Y., Wang Z.D. and Zhang F.C., Imbalanced superfluid state in an annular disk, Journal of Physics: Condensed Matter. Bristol, IOP Publishing Limited, 2009, 21: 355701: 1-8. |
| Researcher : Ye M |
| List of Research Outputs |
| Bai Y., Ye M. and Wang Z.D., Entanglement monogamy and entanglement evolution in multipartite systems, Physical Review A (Brief Reports). New York, The American Physical Society, 2009, 80: 044301: 1-4. |
| Ye M., Bai Y.K., Lin X.M. and Wang Z.D., Exploration of nonlocalities in ensembles consisting of bipartite quantum states, Physical Review A (Brief Reports). New York, The American Physical Society, 2010, 81: 014303: 1-4. |
| Researcher : Yip CT |
| List of Research Outputs |
| Chen X., Yip C.T., Fung M.K., Djurisic A. and Chan W.K., GaN-nanowire-based dye-sensitized solar cells, Applied Physics A: Materials Science & Processing. Springer, 2010, 100: 15-19. |
| Yip C.T., Effect of morphologies and electronic properties of metal oxide nanostructure layer on dye sensitized solar cells. Hong Kong, The University of Hong Kong, 2010, 1-102. |
| Researcher : Yu Y |
| List of Research Outputs |
| Cheng K.S., Yu Y. and Harko T.C., High-redshift gamma-ray bursts: Observational signatures of superconducting cosmic strings?, Physical Review Letters. New York, The American Physical Society, 2010, 104: 241102: 1-4. |
| Yu Y., Cheng K.S. and Cao X.F., The role of newly born magnetars in gamma-ray burst X-ray afterglow emission: Energy injection and internal emission , The Astrophysical Journal. The American Astronomical Society, 2010, 715: 477-484. |
| Researcher : Yung BHK |
| List of Research Outputs |
| Nakashima J., Kwok S., Zhang Y., Hsia C., Chong S.N., Yung B.H.K., Koning N. and Deguchi S., Telescope Time of the NRO 45m Telescope (Project Title: 3D Structure of the Helix: Verification of the Bicone Model), Nobeyama Radio Observatory, National Astronomical Observatory of Japan. 2010. |
| Researcher : Yung HKB |
| List of Research Outputs |
| Imai H., Yung H.K.B., Nakashima J., Deguchi S., Diamond P.J. and Kwok S., High Velocity Precessing Jets from the Water Fountain IRAS 18286−0959 Revealed by VLBA Observations, East Asia VLBI Workshop 2010. . |
| Nakashima J., Deguchi S., Imai H., Kwok S., Koning N., Yung H.K.B., Zhang Y. and Chong S.N., Telescope Time of CARMA (Project Title: CO Mapping of the Water Fountain Object IRAS 18286-0959) , Combined Array for Research in Millimeter-wave Astronomy (CARMA). 2010. |
| Researcher : Zhang F |
| Project Title: | The 8th International Conference on Materials and Mechanisms of Superconductivity and High Temperature Superconductors (M2S-HTSC-VIII) Rotational Symmetry Breaking in Sodium Doped Cuprates |
| Investigator(s): | Zhang FC |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 07/2006 |
| Abstract: |
| N/A |
| Project Title: | Theoretical study of magnetic properties in high temperature superconductivity |
| Investigator(s): | Zhang FC |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2007 |
| Abstract: |
| The main goal of this project is to study the interplay between the anti-ferromagnetism and superconductivity in the high temperature superconducting copper oxides. We propose to study this by using a plain vanilla resonating valence bond theory, where a simple microscopic model captures strong electron correlations and the ground state is a Gutzwiller projected superconducting pairing state with the possible anti-ferromagnetic long range order. We will theoretically study the possible anti-ferromagnetism in the doped copper oxide plane with neighboring anti-ferromagnetically ordered layers. We propose to use a t-J model with additional staggered Zeeman term to represent the magnetic coupling from the neighboring planes. The calculation will be compared with the recent nuclear magnetic resonance experiments on the under-doped five-layered Hg-based cuprates. We will study the superconducting instability of very lightly doped t-J model predominantly antiferromagnetic in the presence of a pairing field. This is to model the possible superconductivity in the inner planes of the multi-layered Hg-compounds. We will develop a moment method to calculate the two-particle correlation function within the plain vanilla resonating valence bond theory. The moment method is expected to be very useful to study strongly correlated systems by using the ground states of the systems. We will use the results calculated from the moment method described in objective 4 to estimate the magnetic scattering functions of the Gutzwiller projected d-wave BCS pairing ground state by using a phenomenological theory. The results will be compared with the neutron scattering data of the magnetic excitations. |
| Project Title: | Computational Sciences |
| Investigator(s): | Zhang FC, Chew WC |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding for Strategic Research Theme |
| Start Date: | 07/2008 |
| Completion Date: | 06/2011 |
| Abstract: |
| n/a |
| Project Title: | Theoretical study of anisotropic states in high temperature superconducting copper oxides |
| Investigator(s): | Zhang FC |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2008 |
| Abstract: |
| 1) To theoretically study the energies of various anisotropic states by using the variational method within the t-J model. 2) To study the effect of the lattice structure of the low temperature tetregonal phase of LaBaCuO at doping 1/8 to the parameters in the microscopic models for electrons in Cu-oxide plane. 3) To study the possibility of the anisotropic state with stripe charge orderings induced by the charge potentials and/or anisotropic and non-uniform hopping integrals in the t-J model. 4) To study the possibility of the stripe state with both charge and incommensurate spin orderings due to the charge potentials and/or anisotropic and non-uniform hopping integrals in the t-J model. 5) To compare theoretical calculations with the experimental results on the stripe phase. |
| Project Title: | Transport property and thermoelectric effect of iron-based superconductors |
| Investigator(s): | Zhang FC |
| Department: | Physics |
| Source(s) of Funding: | Travel Grants for NSFC/RGC JRS |
| Start Date: | 12/2008 |
| Abstract: |
| Travel grants for NSFC/RGC JRS |
| Project Title: | Nano-Spintronics – Quantum Control of Electron Spins in Semiconductors |
| Investigator(s): | Zhang FC, Chan WK, Cui X, Shen SQ, Xie MH |
| Department: | Physics |
| Source(s) of Funding: | Collaborative Research Fund (CRF) - Group Research Project |
| Start Date: | 03/2009 |
| Abstract: |
| To form a strong research team of spintronics in Hong Kong with the strength in close collaborations between theory and experiment; to explore the possibility of electron spin control and manipulation in semiconductors by electric field; to theoretically and experimentally study the quantum charge transport assisted by optically injected or assisted spin current: to explore the possibility for the non-magnetic optical spin source and related devices |
| Project Title: | Visiting Research Professors Scheme 2009-10 |
| Investigator(s): | Zhang FC |
| Department: | Physics |
| Source(s) of Funding: | Visiting Research Professors Scheme |
| Start Date: | 09/2009 |
| Abstract: |
| To support the appointment of Professor Hong Guo as Visiting Research Professor in the Department of Physics. |
| Project Title: | Theory for iron based high temperature superconductivity |
| Investigator(s): | Zhang FC |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 10/2009 |
| Abstract: |
| 1) To study multi-orbital Hubbard model, which is relevant to the iron based superconductors. 2) To study the superconductivity of the multi-orbital Hubbard model in two-dimensional space for the iron based compounds, and to derive an effective pairing Hamiltonian for the doped carriers with three or more orbitals by using a perturbation theory from strong coupling point of view. 3) To theoretically study competition and possible coexistence between superconductivity and antiferromagnetism. 4) To theoretically study Co- or Ni- impurity effect in the Fe-based superconductors. 5) To study various interesting phenomena such as the relative phase of the order parameters on different Fermi pockets by using phenomenological theory. |
| Project Title: | Transport Property and Thermoelectric effect of iron-based superconductors |
| Investigator(s): | Zhang FC, Chen W |
| Department: | Physics |
| Source(s) of Funding: | NSFC/RGC Joint Research Scheme |
| Start Date: | 01/2010 |
| Abstract: |
| 1) To investigate the existence of the quantum phase transition in the region with highest possibility by tuning the chemical pressure introduced by element substitution. Try to find new doping method and prove the generality of the phase diagram. 2) To improve the understanding to the ordered state by probing the properties of the elementary excitations with the measurements of Nernst effects etc. 3) To illustrate the rule of the evolution of different ordered phases with changing the correlation length of the electrons. Try to understand the multi-band effect of the system, explain the phase diagram, and even the superconducting mechanism. |
| Project Title: | Theory, Modeling, and Simulation of Emerging Electronics |
| Investigator(s): | Zhang FC, Chen G, Chew WC, Wang J, Guo H |
| Department: | Physics |
| Source(s) of Funding: | Areas of Excellence Scheme |
| Start Date: | 01/2010 |
| Abstract: |
| n/a |
| Project Title: | Quantum Order in Novel Materials: Superconductivity and Topological Order |
| Investigator(s): | Zhang FC, Ng TK, Shen SQ, Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | Collaborative Research Fund (CRF) - Group Research Project |
| Start Date: | 06/2010 |
| Abstract: |
| (1) Understanding the physical properties of pnictide superconductors and topological insulators; in particular, the nature of quantum order in these materials and the associated experimental signatures; (2) Studying the phenomenology associated with the unusual properties of the materials, in particular the physical consequences of the proposed s state in pnictides superconductors and the unique topological edge excitations in topological insulators under different physical settings; and (3) Investigating the possible existence of general topologically ordered states and understanding the general mathematical structure behind quantum topological order and their implications in quantum information. |
| List of Research Outputs |
| Zhang F., Photoluminescence and reflectance spectra of Si-doped GaN epilayers. Hong Kong, The University of Hong Kong, 2009, 1-79. |
| Researcher : Zhang F |
| List of Research Outputs |
| Zhang F., Photoluminescence and reflectance spectra of Si-doped GaN epilayers. Hong Kong, The University of Hong Kong, 2009, 1-79. |
| Researcher : Zhang FC |
| Project Title: | The 8th International Conference on Materials and Mechanisms of Superconductivity and High Temperature Superconductors (M2S-HTSC-VIII) Rotational Symmetry Breaking in Sodium Doped Cuprates |
| Investigator(s): | Zhang FC |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 07/2006 |
| Abstract: |
| N/A |
| Project Title: | Theoretical study of magnetic properties in high temperature superconductivity |
| Investigator(s): | Zhang FC |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2007 |
| Abstract: |
| The main goal of this project is to study the interplay between the anti-ferromagnetism and superconductivity in the high temperature superconducting copper oxides. We propose to study this by using a plain vanilla resonating valence bond theory, where a simple microscopic model captures strong electron correlations and the ground state is a Gutzwiller projected superconducting pairing state with the possible anti-ferromagnetic long range order. We will theoretically study the possible anti-ferromagnetism in the doped copper oxide plane with neighboring anti-ferromagnetically ordered layers. We propose to use a t-J model with additional staggered Zeeman term to represent the magnetic coupling from the neighboring planes. The calculation will be compared with the recent nuclear magnetic resonance experiments on the under-doped five-layered Hg-based cuprates. We will study the superconducting instability of very lightly doped t-J model predominantly antiferromagnetic in the presence of a pairing field. This is to model the possible superconductivity in the inner planes of the multi-layered Hg-compounds. We will develop a moment method to calculate the two-particle correlation function within the plain vanilla resonating valence bond theory. The moment method is expected to be very useful to study strongly correlated systems by using the ground states of the systems. We will use the results calculated from the moment method described in objective 4 to estimate the magnetic scattering functions of the Gutzwiller projected d-wave BCS pairing ground state by using a phenomenological theory. The results will be compared with the neutron scattering data of the magnetic excitations. |
| Project Title: | Computational Sciences |
| Investigator(s): | Zhang FC, Chew WC |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding for Strategic Research Theme |
| Start Date: | 07/2008 |
| Completion Date: | 06/2011 |
| Abstract: |
| n/a |
| Project Title: | Theoretical study of anisotropic states in high temperature superconducting copper oxides |
| Investigator(s): | Zhang FC |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 07/2008 |
| Abstract: |
| 1) To theoretically study the energies of various anisotropic states by using the variational method within the t-J model. 2) To study the effect of the lattice structure of the low temperature tetregonal phase of LaBaCuO at doping 1/8 to the parameters in the microscopic models for electrons in Cu-oxide plane. 3) To study the possibility of the anisotropic state with stripe charge orderings induced by the charge potentials and/or anisotropic and non-uniform hopping integrals in the t-J model. 4) To study the possibility of the stripe state with both charge and incommensurate spin orderings due to the charge potentials and/or anisotropic and non-uniform hopping integrals in the t-J model. 5) To compare theoretical calculations with the experimental results on the stripe phase. |
| Project Title: | Transport property and thermoelectric effect of iron-based superconductors |
| Investigator(s): | Zhang FC |
| Department: | Physics |
| Source(s) of Funding: | Travel Grants for NSFC/RGC JRS |
| Start Date: | 12/2008 |
| Abstract: |
| Travel grants for NSFC/RGC JRS |
| Project Title: | Nano-Spintronics – Quantum Control of Electron Spins in Semiconductors |
| Investigator(s): | Zhang FC, Chan WK, Cui X, Shen SQ, Xie MH |
| Department: | Physics |
| Source(s) of Funding: | Collaborative Research Fund (CRF) - Group Research Project |
| Start Date: | 03/2009 |
| Abstract: |
| To form a strong research team of spintronics in Hong Kong with the strength in close collaborations between theory and experiment; to explore the possibility of electron spin control and manipulation in semiconductors by electric field; to theoretically and experimentally study the quantum charge transport assisted by optically injected or assisted spin current: to explore the possibility for the non-magnetic optical spin source and related devices |
| Project Title: | Visiting Research Professors Scheme 2009-10 |
| Investigator(s): | Zhang FC |
| Department: | Physics |
| Source(s) of Funding: | Visiting Research Professors Scheme |
| Start Date: | 09/2009 |
| Abstract: |
| To support the appointment of Professor Hong Guo as Visiting Research Professor in the Department of Physics. |
| Project Title: | Theory for iron based high temperature superconductivity |
| Investigator(s): | Zhang FC |
| Department: | Physics |
| Source(s) of Funding: | General Research Fund (GRF) |
| Start Date: | 10/2009 |
| Abstract: |
| 1) To study multi-orbital Hubbard model, which is relevant to the iron based superconductors. 2) To study the superconductivity of the multi-orbital Hubbard model in two-dimensional space for the iron based compounds, and to derive an effective pairing Hamiltonian for the doped carriers with three or more orbitals by using a perturbation theory from strong coupling point of view. 3) To theoretically study competition and possible coexistence between superconductivity and antiferromagnetism. 4) To theoretically study Co- or Ni- impurity effect in the Fe-based superconductors. 5) To study various interesting phenomena such as the relative phase of the order parameters on different Fermi pockets by using phenomenological theory. |
| Project Title: | Transport Property and Thermoelectric effect of iron-based superconductors |
| Investigator(s): | Zhang FC, Chen W |
| Department: | Physics |
| Source(s) of Funding: | NSFC/RGC Joint Research Scheme |
| Start Date: | 01/2010 |
| Abstract: |
| 1) To investigate the existence of the quantum phase transition in the region with highest possibility by tuning the chemical pressure introduced by element substitution. Try to find new doping method and prove the generality of the phase diagram. 2) To improve the understanding to the ordered state by probing the properties of the elementary excitations with the measurements of Nernst effects etc. 3) To illustrate the rule of the evolution of different ordered phases with changing the correlation length of the electrons. Try to understand the multi-band effect of the system, explain the phase diagram, and even the superconducting mechanism. |
| Project Title: | Theory, Modeling, and Simulation of Emerging Electronics |
| Investigator(s): | Zhang FC, Chen G, Chew WC, Wang J, Guo H |
| Department: | Physics |
| Source(s) of Funding: | Areas of Excellence Scheme |
| Start Date: | 01/2010 |
| Abstract: |
| n/a |
| Project Title: | Quantum Order in Novel Materials: Superconductivity and Topological Order |
| Investigator(s): | Zhang FC, Ng TK, Shen SQ, Wang ZD |
| Department: | Physics |
| Source(s) of Funding: | Collaborative Research Fund (CRF) - Group Research Project |
| Start Date: | 06/2010 |
| Abstract: |
| (1) Understanding the physical properties of pnictide superconductors and topological insulators; in particular, the nature of quantum order in these materials and the associated experimental signatures; (2) Studying the phenomenology associated with the unusual properties of the materials, in particular the physical consequences of the proposed s state in pnictides superconductors and the unique topological edge excitations in topological insulators under different physical settings; and (3) Investigating the possible existence of general topologically ordered states and understanding the general mathematical structure behind quantum topological order and their implications in quantum information. |
| List of Research Outputs |
| Chen W., Yang K., Zhou Y. and Zhang F.C., Theory for superconductivity in iron pnictides at large Coulomb U limit, Frontiers of Physics in China. Higher Education Press, 2009, 4: 447-454. |
| Chen W., Ma F.J., Lu Z.Y. and Zhang F.C., p junction to probe antiphase s-wave pairing in iron pnictide superconductors, Physical Review Letters. New York, The American Physical Society, 2009, 103: 207001: 1-4. |
| Dai J., Lu H., Yang C., Shen S.Q., Zhang F.C. and Cui X., Magnetoelectric photocurrent generated by direct interband transitions in InGaAs/InAlAs two-dimensional electron gas, Physical Review Letters. New York, The American Physical Society, 2010, 104: 246601: 1-4. |
| Feng X., Chen W., Gao J., Wang Q.H. and Zhang F.C., Anderson impurity in a helical metal, Physical Review B. New York, The American Physical Society, 2010, 81: 235411: 1-5. |
| Gao J., Chen W., Xie X.C. and Zhang F.C., In-plane noncollinear exchange coupling mediated by helical edge states in quantum spin Hall systems, Physical Review B (Rapid Communications). New York, The American Physical Society, 2009, 80: 241302: 1-4. |
| Jiang Z., Shen S.Q. and Zhang F.C., Disorder effect of resonant spin Hall effect in a tilted magnetic field, Physical Review B. New York, The American Physical Society, 2009, 80: 195301: 1-6. |
| Wang Q.H., Wang D. and Zhang F.C., Electronic structure near an impurity and terrace on the surface of a three-dimensional topological insulator, Physical Review B. New York, The American Physical Society, 2010, 81: 035104: 1-7. |
| Yang K.Y., Chen W., Rice T.M. and Zhang F.C., Origin of the checkerboard pattern in scanning tunneling microscopy maps of underdoped cuprate superconductors, Physical Review B. New York, The American Physical Society, 2009, 80: 174505: 1-7. |
| Ye F., Chen Y., Wang Z.D. and Zhang F.C., Imbalanced superfluid state in an annular disk, Journal of Physics: Condensed Matter. Bristol, IOP Publishing Limited, 2009, 21: 355701: 1-8. |
| Researcher : Zhang L |
| List of Research Outputs |
| Wang B., Xing Y., Zhang L. and Wang J., Transient dynamics of molecular devices under a steplike pulse bias, Physical Review B (Rapid Communications). New York, The American Physical Society, 2010, 81: 121103: 1-4. |
| Zhang L., First principle calculation: Current density in AC electric field. Hong Kong, The University of Hong Kong, 2009, 1-67. |
| Researcher : Zhang Y |
| Project Title: | The Infrared Morphologies of Planetary Nebulae |
| Investigator(s): | Zhang Y, Kwok S, Nakashima J |
| Department: | Physics |
| Source(s) of Funding: | Seed Funding Programme for Basic Research |
| Start Date: | 03/2010 |
| Abstract: |
| As a low and intermediate mass star reaches the end of its lives, its envelope is ejected into the space, and at the same time the temperature of the stellar core quickly increases. When the central star is hot enough to photo-ionize the surrounding gaseous shell, a planetary nebula (PN) is formed. We have learned that PNs contain ionized gas, molecular gas, and dust. These different nebular components can be detected in different wavelengths, and serve as crucial probes of the interaction between stellar nucleosynthetic products and chemical evolution of galaxies. In this proposal, we plan to perform an infrared study of PNs, aiming at finding new PNs and investigating the properties of molecular gas, ionized gas, and dust grains and their interaction. Highly obscured PNs, which are abundantly present in the Galaxy, are very faint or even invisible at optical wavelengths. Being free from extinction of interstellar dust, infrared observations have certain advantage to study these optically faint/invisible PNs. We proposal to use infrared images to search for new PNs that have not been found in previous optical surveys. Accurate PN designation is impossible without multi-wavelength observations. We will use these infrared data to confirm/reject PNs since they can provide insight into the heavily obscured regions. Although it has been established that complex molecules, such as polycyclic aromatic hydrocarbons (PAHs) are being actively processed in PNs and dust grains play an important role in nebular chemistry, the details of dust processing in PNs is exceedingly complex and far to be completely understood. Infrared observations provide an unique tool to investigate the dust processing in PNs. We will obtain nebular images at several different infrared bands. This enables to study the formation and destruction of different dust grains. Extensive optical observations (e.g. by Hubble Space Telescope) have revealed that PNs have diverse morphologies. However, the physical cause leading to the various structure is poorly known. We plan to collect infrared images of PNs in an evolutionary sequence. Combining with optical and radio data (which respectively trace ionized and molecular gas), we can study the mass-loss history of PNs, and the interaction between different nebular components. |
| Project Title: | The Frontier on Interstellar Medium Molecular line surveys in the envelopes of evolved stars |
| Investigator(s): | Zhang Y |
| Department: | Physics |
| Source(s) of Funding: | URC/CRCG - Conference Grants for Teaching Staff |
| Start Date: | 06/2010 |
| Completion Date: | 06/2010 |
| Abstract: |
| N/A |
| List of Research Outputs |
| Deguchi S., Nakashima J., Zhang Y., Chong S.N., Koike K. and Kwok S., SiO and H2O maser observations of red supergiants in star clusters embedded in the galactic disk, Publications of the Astronomical Society of Japan. Astronomical Society of Japan, 2010, 62: 391-407. |
| He J.H., Dinh-v-Trung , Kwok S., Muller H.S.P., Zhang Y., Hasegawa T., Peng T.C. and Huang Y.C., 1.3 and 2mm survey of IRC+10216 (He+, 2008), VizieR Online Data Catalog. 2009. |
| Kwok S., Chong S.N., Hsia C., Zhang Y. and Koning N.A., Discovery of a Multipolar Structure with an Equatorial Disk in NGC 6072, The Astrophysical Journal. 2010, 708: 93-100. |
| Nakashima J., Deguchi S., Imai H., Kwok S., Koning N., Yung H.K.B., Zhang Y. and Chong S.N., Telescope Time of CARMA (Project Title: CO Mapping of the Water Fountain Object IRAS 18286-0959) , Combined Array for Research in Millimeter-wave Astronomy (CARMA). 2010. |
| Nakashima J., Kwok S., Zhang Y., Hsia C., Chong S.N., Yung B.H.K., Koning N. and Deguchi S., Telescope Time of the NRO 45m Telescope (Project Title: 3D Structure of the Helix: Verification of the Bicone Model), Nobeyama Radio Observatory, National Astronomical Observatory of Japan. 2010. |
| Zhang Y. and Liu X...-.W..., Determination of Elemental Abundances in Photoionized Gaseous Nebulae, 光致电离气体星云的元素丰度测量, 10000 Selected Problems in Sciences ---- Astronomy. 10000个科学难题-天文学卷, 2010, 259. |
| Zhang Y., Molecular line surveys in the envelopes of evolved stars, The Frontier on Interstellar Medium ---- 40th Anniversary on the Discovery of CO in ISM. 2010. |
| Zhang Y. and Kwok S., Planetary Nebulae Detected in the Spitzer Space Telescope Glimpse II Legacy Survey, The Astrophysical Journal. The American Astronomical Society, 2009, 706: 252. |
| Zhang Y., Nakashima J., Kwok S., Chong S.N. and Deguchi S., Telescope Time of the NRO 45m Telescope (Project Title: A Spectral Line Survey in the 7mm Window toward the Highly Evolved Carbon Star CIT 6), Nobeyama Radio Observatory, National Astronomical Observatory of Japan. 2010. |
| Zhang Y., The Origin of Diffuse Interstellar Bands, 星际弥散带的起源, 10000 Selected Problems in Sciences ---- Astronomy . 10000个科学难题-天文学卷, 2010, 342. |
| Zhang Y., The planetary nebulae in the GLIMPSE legacy survey, Cosmic dust. 2009. |
| Researcher : Zhao H |
| List of Research Outputs |
| Zhao H., Lecture/presentation: "Photophysics of single-walled carbon nanotubes", South China Normal University. 2009. |
| Researcher : Zhu C |
| List of Research Outputs |
| Fan J., Zhu C., Fung S.H.Y., Zhong Y.C., Wong K.S., Xie Z., Brauer G., Anwand W., Skorupa W., To C.K., Yang B., Beling C.D. and Ling F.C.C., Arsenic doped p-type zinc oxide films grown by radio frequency magnetron sputtering, Journal of Applied Physics. New York, American Institute of Physics, 2009, 106: 073709: 1-6. |
| Researcher : Zhu S |
| List of Research Outputs |
| Xue Z., Zhu S. and Wang Z.D., Quantum computation in a decoherence-free subspace with superconducting devices, European Physical Journal D. EDP Sciences, 2009, 55: 223-228. |