Chủ tịch danh dự Chủ tịch Hội nghị Ban Tổ chức Ban ... - Viện Vật lý

(3) Hanoi Advanced School of Science and Technology, Hanoi
University of Science and Technology, Building F No 40 Ta Quang
Buu Street, Hanoi, Vietnam
We present a study of the effects of a magnetic field on the
electronic structure and transport properties of graphene and
graphene nanoribbons with two typical edge shapes, namely the
zigzag and the armchair. In our calculations an empirical tightbinding
description in the nearest neighbor coupling approximation
is used to describe the graphene nanoribbons. The magnetic field is
included by using the conventional Peierls substitution which leads
to a phase factor for the hoping parameter between two lattice
nodes. The dependence of the energy on the wave vector along the
ribbons length or the dissipation law is then calculated just by
diagonalizing a Hamiltonian. However, the transport properties of these
systems are investigated by using the non-equilibrium Green’s function
(NEGF) method. Obtained results show that the magnetic field almost
does not cause any significant effects for narrow graphene nanoribbons,
but for the larger one (>30 nm) it can significantly quantize the electronic
states of graphene and graphene nanoribbons into discrete modes known
as the Landau levels. This quantization is clearly seen in the pictures of the
density of states and/or the transmission coefficient.
Báo cáo Treo
36. Influence of Phonon Confinement on Absorption Power and
Line-Width in a Free-Standing Gaas Quantum Wire
Le Dinh (1), Le Quoc Anh (1) and Tran Cong Phong (1,2)
(1) Departmant of Physcis, Hue University's College of Education, 32
Le Loi, Hue, Viet nam.
(2) National Education Union of Vietnam, 02 Trinh Hoai Duc, Dong
Da, Ha noi, Viet Nam
Based on state-independent projection technique (SIPT) we
calculate analytical expressions of conductivity tensor and
absorption power in cylindrical quantum wires (CQW) due to
electron-longitudinal optical (LO) phonon interaction. Both
electrons and phonons are confined in the CQW and the numerical
results are presented for free-standing GaAs quantum wires. From
graphs of the absorption power we obtain line-widths as profile of
curves. The dependence of the absorption power and the line-widths
Hội nghị Vật lý lý thuyết toàn quốc lần thứ 35
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on the temperature, the radius of the CQW are obtained.
Comparisons between the value of the absorption powers and the
line-widths in the case of confined phonons and bulk phonons are
discussed.
Báo cáo Treo
Tp. Hồ Chí Minh, 02-06/8/2010
37. Simple Model for the Indirect Exciton in a Strong Magnetic Field
V.T Hoa, T.T.T. Van, T.T. Thao, P.D. Anh, N.V. Thanh,
and N.A. Viet
Institute of Physics, Vietnam Academy of Science and Technology, 10
Dao Tan, Ba Dinh, Ha Noi
A simple theoretical model for the indirect exciton (type 2) without
and in strong magnetic field is developed, in which the electrons
and hole are separated in two spaces. The stabilize role of a strong
magnetic field is investigated. For comparison the case of exciton
type 2 in InP/GaAs quantum dot was studied and found a good
agreement between theoretical and experimental data.
Báo cáo Treo
38. Conductance and Shot Noise in Gate-Controlled Zigzag
Graphene Nanoribbons
Tran Nguyen Dung
Institute of Physics, Vietnam Academy of Science and Technology, 10
Dao Tan, Ba Dinh, Ha Noi
Using the recursive Green’s function method, we study the ballistic
transport in gated controlled zigzag graphene nanoribbons. The
conductance, the current-voltage characteristics, and the shot noise
have been calculated for ribbons with different widths under a
tuning gate. We observed a step-like structure and an oscillation
behavior of the conductance as a function of the incident energy.
The shot noise value obtained demonstrates the ballistic nature of
the conduction process.
Báo cáo Treo
39. Electron Mobility in a Semiconductor Quantum Wire
Nguyen Nhu Dat (1) and Le Thanh Hai (2)
(1) Institute of Physics, Vietnam Academy of Science and Technology,
10 Dao Tan, Ba Dinh, Ha Noi; (2) Hanoi University of Civil
Engineering
A macroscopic continuum model is used to study the longitudinal
optical phonons in a circular semiconductor quantum wire which is
embeded in a finite thickness barrier. The Hamiltonian describing
the electron-LO-phonon interaction is obtained and used to calculate
the phonon-limited electron mobility by the memory function
approach. Numerical calculations are performed for a typical
GaAs/GaAlAs quantum wire to demonstrate the effect of the barrier
thickness on the electron mobility.
Báo cáo Mieng
40. Effect from Doping of Quantum - Wells on Enhancement of The
Mobility Limited by One-Interface Roughness Scattering
Tran Thi Hai (1), Nguyen Trung Hong (2), Nguyen Huyen
Tung( 3)
(1) Department of Physic, Hanoi National University, 334 Nguyen
Trai, Thanh Xuan, Hanoi, Vietnam
(2) Center for Talent Training, Hanoi University of Technology, 1
Dai Co Viet Road, Hanoi, Vietnam
(3) Institute of Engineering Physics, Hanoi University of Technology,
1 Dai Co Viet Road, Hanoi, Vietnam
We present a theoretical study of the effect from doping of quantum
wells (QW) on enhancement of the mobility limited by oneinterface
roughness scattering. We find that for roughness-related
scattering from two interfaces or from the doping-side interface, the
mobility in a two-side (2S)-doped QW are larger than that in oneside
(1S)-doped, but smaller than that in undoped counterparts. For
scattering
from
substrate-side interface, the 2S-doped QW mobility is smaller than
the 1S-doped QW one. We examine the dependence of the 2Sdoped
QW mobility on the well width, carrier density, and
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Tp. Hồ Chí Minh, 02-06/8/2010