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Analytic expressions for the nonlinear absorptioncoefficient of a strong electromagnetic wave by confinedelectrons in cylindrical quantum wires with parabolicpotential are calculated by using the quantum kineticequation for electrons in two cases: electron-opticalphonon scattering and electron-acoustic phononscattering. The dependence of the nonlinear absorptioncoefficient on the intensity E0 and frequency Ω of theexternal strong electromagnetic wave, the temperature Tof the system, the radius R of wire is obtained. Theanalytic expressions are numerically calculated anddiscussed for GaAs/GaAsAl quantum wires. The resultsare compared with those for the normal bulksemiconductors and quantum well to show the difference.Người trình bày: Nguyễn Quang Báu27. Lo-Phonon-Limited Electron Mobility in a PolarSemiconductor Quantum WireNguyễn Như ĐạtA macroscopic continuum model is used to study thelongitudinal optical phonons in a polar semiconductorquantum wire with circular cross section. The FröhlichHamiltonian describing the electron-phonon interaction isthen obtained and used to calculate the electron mobilitygoverned by confined LO phonons by means of thememory function approach, including the many-particleeffect in the RPA framework. The difference in thebackground dielectric constant of the wire and the barriermaterial is taken into account. Numerical calculations aregiven for a GaAs/GaAlAs quantum wire.Người trình bày: Nguyễn Như Đạt28. Mobility Enhancement In Square Quantum well:Symmetric Modulation of Envelop WaveFunctionTrần Thị Hải, Nguyễn Trung Hồng, NguyễnHuyền Tụng, Đoàn Nhật QuangWe present a theoretical study of the effects fromsymmetric modulation of the envelop wave function onquantum transport in square quantum well (QWs).Within the variational approach, we obtain analyticexpressions for the carrier distribution and theirscattering in double-side doped square QWs. Scatteringby surface roughness and misfit deformation potentialare found significantly weaker than those in thereference single-side doped sample. Thus, symmetricmodulation of the wave-function is proposed as anefficient method for mobility enhancement in squareQWs. The optimization of the conductivity is discussed.Our theory is successful in explaining the recentexperimental data about transport properties, e.g., themobility dependence on the channel width.Người trình bày: Trần Thị Hải29. Phase Transition in Binary Mixture of BoseGasesTrần Hữu Phát, Lê Viết Hòa, Nguyễn Tuấn Anh,Nguyễn Văn LongBased on the Cornwall-Jackiw-Tomboulis (CJT)effective action approach a theoretical formalism isestablished for studying the Bose-EinsteinThành phố Đồng Hới (03- 06/8/2009) Trang 37/ 102 Thành phố Đồng Hới (03- 06/8/2009) Trang 38/ 102