吴明卫
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COLLOQUIA & SEMINARS 2005:
(COLLOQUIUM)"Anomalous Properties of Pd Thin Film due to Quantum Size Effect", Prof. Dr. Qi-Kun Xue (Institute of Physics, CAS), at 4:00 pm, Jan. 7, 2005.
(SEMINAR)"Dynamic Hall resistivity in the presence of Rashba spin-orbit interaction", Prof. Dr. Zhong-Shui Ma (Peking University), at 3:00 pm, Feb. 18, 2005.
Abstract:
The Hall resistivity ($\rho_{xy}$) is discussed in an electronic system with sufficient Rashba coupling and in the absence of external magnetic field. It is found that the off-diagonal component of the resistivity is determined by the reactive part (real part) of the inverse dielectric functions. This is in contrast to any other electrical transport including magnetotransport where all resistivity components (both diagonal and off-diagonal) are determined by the absorptive part (imaginary part) of the inverse dielectric functions.
(COLLOQUIUM)"Uncertainty of the 'Uncertainty Principle'", and "The Sand of Time", Prof. Dr. Ze-Xian Cao (Institute of Physics, CAS), at 3:00 pm, Mar. 18, 2005.
Abstract1:
In quantum mechanics, physical quantities are represented as operators which are not necessarily commutating. For those non-commutating operators there¡¯re no mutual eigenstate, therefore the product of their variances in any given state should have a minimum value, according to the Schwartz inequality in Hilbert space. This is all that the Heisenberg uncertainty principle can tell, but, unfortunately, there¡¯re too many misunderstandings and misinterpretations that confuse the physics students. One particular example is the so-called energy-time uncertainty relation. In this talk the development of uncertainty principle will be scrutinized from scratch.
Abstract2:
The logo for world year of physics 2005 is a sandglass. It is also the illustration of light cone, a fundamental concept in the Einstein¡¯s special relativity which provides us a revolutionary view of space-time. But what is time? Is it real or imaginary, indefinite or cyclic, a parameter or a variable, one dimensional or half-dimensional, translational or having a starting point? All these to-be-or-not-to-be¡¯s indicate the absence of a universal role for time in physics.
(SEMINAR)"Interface formation in organic semiconductor based electronics", Prof. Dr. Yong-Li Gao (University of Rochester, Rochester, NY, USA) at 3:00 pm, June 30, 2005.
Abstract:
Interface properties play an important role in semiconductor devices. With organic based semiconductor devices, such as organic light emitting diodes and organic thin film transistors, the role of interface properties is uniquely different than inorganic semiconductors. We have investigated the interface formation in organic semiconductor devices using photoemission spectroscopy and other surface sensitive probes. These observations allow us to discuss the mechanisms that can be used to describe the interface between organic semiconductors and metals or dielectrics, such as charge transfer and interface dipole formation, and relate these effects to the energy level alignment at interfaces and the device performance.
(COLLOQUIUM)"Theoretical challenge in magnetic information technology", Prof. Dr. Shu-Feng Zhang (University of Missouri-Columbia, USA) at 3:00 pm, July 3, 2005.
Abstract:
I will discuss the current research in current-driven magnetization dynamics in magnetic nanostructures. At a sufficiently large current density, the spin angular momentum transfer leads to magnetization reversal and stable magnetization precessional states. Here we focus on a novel state of affair: the current-driven dynamic phase transition in ferromagnetic materials.
(SEMINAR)"Spin Polarization and Charge Density Distribution in Diluted Magnetic Semiconductor Multilayered Structures", Prof. Dr. I. C. da Cunha Lima (Instituto de Fisica, Universidade do Estado do Rio de Janeiro, Brazil) at 3:00 pm, August 21, 2005.
(SEMINAR)"All-optical injection of spin currents in semiconductors", Prof. Dr. John E. Sipe (University of Toronto, Canada) at 3:00 pm, August 22, 2005.
Abstract:
It has been understood for years that spin polarized currents in semiconductors can be generated by optically injecting spin polarized carriers and then dragging them with a bias voltage. But only recently has it been generally appreciated, and observed experimentally, that spin currents can be optically injected directly. Here the currents appear on the time scale of the injecting pulse or pulses, which typically is on the order of only 100 femtoseconds. Particularly interesting are scenarios where pure spin currents are injected, in which there is no net spin or electrical current generated, but rather there is a "sorting" of injected carriers by their spin, with carriers of one spin sent in one direction and those of the opposite in the other. Strategies for accomplishing this include the quantum interference of one- and two-photon absorption processes across the band gap, and even scenarios involving the use of only a single laser beam. More recent suggestions involve the use of Raman scattering or far infrared absorption in doped semiconductors, and the possibility of generating an AC pure spin current through the excitation of particular superpositions of exciton states. I will review our theoretcial calculations of these effects, and some of the experimental results of our collaborators, Professor Henry van Driel at the University of Toronto and Professor Arthur Smirl at the University of Iowa.
(COLLOQUIUM) "From Phase Transitions and Critical Phenomena to Emergent Phenomena", Prof. Lu Yu (Member of Chinese Academy of Sciences and The Third World Academy of Sciences, Institute of Theoretical Physics, CAS) at 2:30 pm, Oct. 21, 2005.
(SEMINAR) "Experimental measurement of spin dynamics and spin coherence dynamics in bulk intrinsic GaAs", Prof. Dr. T. S. Lai (Sun Yat-Sen University), at 2:30 pm, Oct. 23, 2005.
Abstract:
Experimental methods to measure spin dynamics in semiconductor and ferromagnetic films are reviewed. New elliptically polarized absorption saturation spectroscopy is developed and used to investigate spin coherence dynamics in bulk intrinsic GaAs. Experimental results on temperature and photon energy dependences are given.
(SEMINAR) "Annealing effect on (Ga,Mn)As and growth of a thicker zincblende CrSb layer", Prof. Dr. J. H. Zhao (Institute of Semiconductors, CAS), at 10:00 am, Oct. 25, 2005.
(SEMINAR) "Investigation on spin polarized injection into conjugated polymer", Prof. Dr. S. J. Xie (School of Physics and Microelectronics, Shandong University), at 2:30 pm, Nov. 15, 2005.
(SEMINAR) "High doping oxide magnetic semiconductor", Prof. Dr. S. S. Yan (School of Physics and Microelectronics, Shandong University), at 3:30 pm, Nov. 15, 2005.
