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Nguyễn Quang Báu, Nguyễn Văn Hiếu, NguyễnThị Thúy, Trần Công PhongThe acoustoelectric effect in a superlattice (SL) isinvestigated for an acoustic wave whose wavelength =/qis smaller than the mean free path l of the electrons andhypersound in the region ql. (where q is the acousticwave number). A nonlinear dependence of theacoustoelectric current jac on the constant electric fieldE is obtained by using classical kinetic Boltzman’sequation. Caculated in the case relaxation time ofmomentum is constant approximation. Numericalcaculations is done, and the result is discussed for atypical GaAs/AlAs SL. It is noted that when the electricfield is negative the current jac falls, reaches aminimum and rises. On the other hand, when theelectric field is positive the current increases, reaches amaximum and then falls off. A similar observation hasbeen noted acoustoelectric interaction in a multilayeredstructure resulting from the analysis of Si/SiO2structure. The dominant mechanism for such a behavioris attributed to the periodicity of the energy spectrum ofelectron along the SL axis.Người trình bày: Nguyễn Văn Hiếu44. Generalization of the Dirac and YangMonopoles to a 9-Dimensional Space – a Non-Abelian SO(8) MonopoleLê Văn Hoàng, Phan Ngọc Hưng, Nguyễn LêĐăngThành phố Đồng Hới (03- 06/8/2009) Trang 49/ 102We generalize the Dirac and Yang monopoles to a 9-dimensional space and have found that it is a non-Abelian SO(8) monopole. The explicit form of themonopole vector potential is given and the boundsystem composed of the found monopole coupled to aparticle by the SO(8) and Coulomb interaction isconsidered. We have found also that the system has theSO(10,2) dynamical symmetry.Người trình bày: Lê Văn Hoàng45. Magneto-phonon Resonance in QuantumWells with Parabolic PotentialBùi Đình Hợi, Trần Công Phong, Võ Thành LâmThe linear dc magneto-conductivity parallel to the walls ofa parabolic quantum well, with a magnetic field$\bold{B}=B \hat{z}$ applied normal to its barriers, isevaluated for electron – optical phonon interaction. Foroptical and polar optical phonons, the magnetoconductivityoscillates as a function of the magnetic fieldwith resonances occuring when $P \omega_c =\omega_0$, where $\omega_c$, $\omega_0$ arecyclotron and optical phonon frequencies, respectively,and where $P$ is an integer. The analytic results arenumerically evaluated to show explicitly the dependence ofmagneto-conductivity on the magnetic field, theconfinement frequency, and the temperature of the system.Người trình bày: Bùi Đình Hợi46. The Effect of Confined Phonons on theNonlinear Absorption Coefficient of a StrongThành phố Đồng Hới (03- 06/8/2009) Trang 50/ 102