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COLLOQUIA & SEMINARS 2004：
 

1. (SEMINAR) "Magnetic Transport in Semiconductors driven by Intense Terahertz Fields", Associate Prof. Dr. Shi-Yong Liu (Department of Applied Physics, Shanghai Jiao-Tong University), at 4:00 pm, March 15, 2004.
   

2. (SEMINAR) "Electronic structure and optical properties of the Co-doped anatase TiO2 studied from first principles", Prof. Dr. Jin-Ming Dong (Department of Physics, Nanjing University), at 4:00 pm, March 22, 2004.

1. Abstract:
   The Co-doped anatase TiO2, a recently discovered room-temperature ferromagnetic insulator, has been studied by the first-principles calculations in the pseudo-potential plane-wave formalism within the local-spin-density approximation (LSDA), supplemented by the full-potential linear augmented plane wave (FP-LAPW) method. Emphasis is placed on dependence of its linear optical properties on the Co-doping concentration and oxygen vacancy in the system in order to pursue the origin of its ferromagnetism. In the case of substitutional doping of Co for Ti,  our calculated results are well consistent with the experimental data, showing that Co is in its low spin state. Also, it is shown that the oxygen vacancy has larger effect on both the electronic structure and optical properties than the Co-doping concentration.

3. (SEMINAR) "Spin injection into semiconductor", Prof. Dr. Ke Xia (State Key Laboratory for Surface Physics, Institute of Physics, Chinese Academy of Sciences), at 4:00 pm, March 24, 2004.

1. Abstract:
   In our tight-binding muffin-tin-orbital (TB-MTO) transport formalism, the scattering states are calculated explicitly so we are able to perform ``channel decomposition'' of the scattering induced by specular interfaces, interface disorder etc. Getting spin imbalance in the high carrier mobility semiconductor is essential for the developing spintronics. Spin-injection from ferromagnetic transition metal to semiconductor, which holds the promise for the room temperature application, is obstructed by the large resistivity difference between metal and semiconductor. Based on the method mentioned above, we studied the spin-injection through Fe|GaAs interfaces. The specular scattering due to band mismatch at interface and the diffusive scattering due to interface disorder are considered on the equate footing. The suggestion of the "interface engineering" on the Fe|GaAs system is also reported.

4. (SEMINAR) "Lattice Boltzmann Method and its Applications in Blood Flow and DNA-Water Flow", Prof. Dr. Hai-Ping Fang (Shanghai Institute of Applied Physics, Chinese Academy of Sciences), at 4:00 pm, March 29, 2004.
   

5. (SEMINAR) "Electromagnetically Induced Transparency In Strongly Coupled Exciton-Phonon Systems", Prof. Dr. K. D. Zhu (Department of Applied Physics, Shanghai Jiao-Tong University), 4:00 pm, April 2, 2004.
   

6. (SEMINAR) "Kondo effect in artificial system", Prof. Dr. Qing-Feng Sun (Institute of Physics, Chinese Academy of Sciences), at 4:00 pm, April 5, 2004.

1. Abstract:
   In this talk, I will report our recent theoretical investigations of quantum transport through mesoscopic systems. I will mainly focus on the Kondo effect which is a prototypical many-body correlation effect in condensed matter. Its recent observation in quantum dots and other artificial systems has generated a great deal of theoretical and experimental excitement. I will present theoretical results on the excess Kondo resonances in normal-superconducting hybrid devices; on how Kondo effect is influenced by spin polarized conduction electrons; on the competition of the Kondo effect and the RKKY interaction in double quantum dots connected by a quantum wire, as well as on other related issues.

7. (COLLOQUIUM)"Two Important Issues in Low Temperature Plasma Physics: Electron energy distribution function and the plasma sheath", Prof. Dr. Yi-Kang Pu (Tsinghua University), at 4:00 pm, April 12, 2004.

1. Abstract:
   Low temperature plasmas (temperature of ions and neutrals are about 300 K or higher) have wide applications in thin film deposition etching and material surface treatment, because of their efficient generation of active neutral species and energetic ions. The concentration of these particles, produced by electron impact processes (ionization, dissociation and excitation) are strongly dependent on electron energy. In most cases, the electrons are not in thermal equilibrium and their energy distribution function (EEDF) is not a Maxwellian. Therefore, investigation of EEDF and its dependence on plasma parameters, such as RF frequency, RF power, discharge pressure, gas composition, etc., is one of the important research topics in low temperature plasma physics.
   
   Plasma sheath is formed at any plasma-surface interface, due to the huge difference of mobilities between electrons and ions. There is a large electrical potential difference between the plasma and the surface. This potential difference accelerates the ions, which bombarding the surface with an energy from a few eV to several hundred eV. Studying sheath dynamics can provide important insight on ion energetics.

8. (SEMINAR)"Quantum dissipation theory and its applications", Associate Prof. Dr. Rui-Xue Xu (USTC), at 4:00 pm, April 26, 2004.
   

9. (SEMINAR)"Spin transport in organic semiconductors", Associate Prof. Dr. Jing Shi (Univ. of Utah), at 4:30 pm, June 7, 2004.
   

10. (SEMINAR)"Unipolar spin diodes and transistors", Prof. Dr. Giovanni Vignale (University of Missouri, USA), at 3:00 pm, June 27, 2004.

1. Abstract:
   Unipolar devices constructed from ferromagnetic semiconducting materials with variable magnetization direction are shown theoretically to behave very similarly to nonmagnetic bipolar devices such as the $p-n$ diode and the bipolar (junction) transistor. Such devices may be applicable for magnetic sensing, nonvolatile memory, and reprogrammable logic.

11. (COLLOQUIUM)"Many-body effects in spin-polarized transport", Prof. Dr. Giovanni Vignale (University of Missouri, USA), at 4:00 pm, June 28, 2004. 

1. Abstract:
   Coulomb correlations between up- and down-spin components of a paramagnetic or uniformly spin-polarized electron liquid are responsible for a number of intriguing phenomena in spin transport. In this seminar I focus on the phenomenon of the ``spin Coulomb drag" -- an intrinsic source of resistance that specifically affects the spin current -- and on the closely related concept of the ``spin mass" -- a novel mass renormalization that modifies the relation between the spin-current carried by a quasiparticle and its momentum. I discuss the influence of these many-body effects on the magnetoresistance and the efficiency of spin-current injection in magnetic multilayers.

12. (SEMINAR)"Recent advances in time-dependent spin density functional theory", Prof. Dr. Giovanni Vignale (University of Missouri, USA), at 3:00 pm, July 5, 2004.

1. Abstract:
   Time-dependent density functional generally suffers from an ultra-nonlocality problem, namely the local density approximation for the exchange-correlation potential always fails, no matter how slowly varying is the density. I show that this problem is particularly severe in time-dependent spin density functional theory, but can be cured by switching to a formulation in which the spin currents are the basic variables. I discuss the physical significance of the new terms that appear in the spin-current dependent functional, and review the progress that has been made in providing explicit expressions for the latter.

13. (COLLOQUIUM)"String-net condensation: A unification of light and elecrtons", Prof. Dr. X. G. Wen (MIT, USA), at 10:00 am, July 27, 2004.

1. Abstract:
   String-net condensation in spin models gives rise to a new form of matter. The collective excitations in string-net condensed phases can behave just like the light and electrons in our vacuum. This suggests that light and electrons (as well as other elementary particles) may originate from a string-net condensation in our vacuum. In addition, the string-net picture indicates how to make artificial photons, artificial electrons, and artificial quarks in condensed matter systems.

14. (COLLOQUIUM)"Strongly Correlated Materials from ab-initio Calculations", Prof. Dr. Vladimir I. Anisimov (Institute of Metal Physics, Russia), at 4:00 pm, Oct. 19, 2004.
    

15. (SEMINAR)"Theory of Bose-Einstein condensates", Prof. Dr. W.M. Liu (Institute of Physics, CAS), at 4:00 pm, Nov. 2, 2004.

1. Abstract:
   Bose-Einstein condensates as dilute gases and strong correlated Bose systems in traps is reviewed from a theoretical perspective. Mean-field theory provides a framework to understand the main features of the condensation and the role of interactions between atoms. Various properties of Bose-Einstein condensates are discussed, including the density profiles, the energy of ground-state configurations, the collective oscillations and the dynamics of expansion, the condensate fraction and the thermodynamic functions. Despite the dil

16. (SEMINAR)"Exciton-phonon interaction and related photoluminescence spectrum", Prof. Dr. S. J. Xiong (Nanjing University) at 4:00 pm, Dec. 1, 2004. 

1. Abstract:
   We investigate excitonic polaron states comprising local exciton and longitudinal optical (LO) phonons and decaying of LO phonons. The series from excited polaron states form a group and have essential contribution to the PL spectrum. By mixing of LO phonons with environal phonon modes, this group reduces to a ``zero-phonon line'' (ZPL), Stokes lines (SL) and anti-Stokes lines. This mixing can be coherent and Fano lineshape may appear. The series from the ground polaron state belongs to another group, including ZPL and SL's, with a redshift to the first group.