共查询到20条相似文献,搜索用时 468 毫秒
1.
M. Geddo R. Ferrini G. Guizzetti M. Patrini S. Franchi P. Frigeri G. Salviati L. Lazzarini 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(1):19-24
We report on a photoreflectance investigation in the 0.8-1.5 eV photon energy range and at temperatures from 80 to 300 K on
stacked layers of InAs/GaAs self-assembled quantum dots (QDs) grown by Atomic-Layer Molecular Beam Epitaxy. We observed clear
and well-resolved structures, which we attribute to the optical response of different QD families. The dependence of the ground
state transition energy on the number of stacked QD layers is investigated and discussed considering vertical coupling between
dots of the same column. It is shown that Coulomb interaction can account for the observed optical response of QD families
with different morphology coexisting in the same sample.
Received 17 November 1999 相似文献
2.
XIE Wen-Fang 《理论物理通讯》2003,39(3):365-368
Making use of the method of few-body physics, the energy spectrum of a four-electron system consisting in a vertically coupled double-layer quantum dot as a function of the strength ofa magnetic field is investigated. Discontinuous ground-state transitions induced by an external magnetic field are shown. We find that, in the strong coupling case, the ground-state transitions depend not only on the external magnetic field B but also on the distance d between double-layer quantum dots. However, in the case of weak coupling, the ground-state transitions occur in the new sequence of the values of the magic angular momentum. Hence, the interlayer separation d and electron-electron interaction strongly affect the ground state of the coupled quantum dots. 相似文献
3.
W.-Y. Ruan H.-F. Cheung 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(3):407-411
A coupled quantum dot system has been studied by numerical diagonalization of the Hamiltonian. Discontinuous ground-state
transitions induced by an external magnetic field have been predicted. Series of magic numbers of angular momentum which minimize
the ground-state electron-electron interaction energy have been discovered. Theoretical explanations derived from the first
principles have been formulated.
Received: 13 July 1997 / Accepted: 7 October 1997 相似文献
4.
D.C. Cabra A. Honecker P. Pujol 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(1):55-73
We analyze the phase diagram of a system of spin-1/2 Heisenberg antiferromagnetic chains interacting through a zig-zag coupling,
also called zig-zag ladders. Using bosonization techniques we study how a spin-gap or more generally plateaux in magnetization
curves arise in different situations. While for coupled XXZchains, one has to deal with a recently discovered chiral perturbation, the coupling term which is present for normal ladders
is restored by an external magnetic field, dimerization or the presence of charge carriers. We then proceed with a numerical
investigation of the phase diagram of two coupled Heisenberg chains in the presence of a magnetic field. Unusual behaviour
is found for ferromagnetic coupled antiferromagnetic chains. Finally, for three (and more) legs one can choose different inequivalent
types of coupling between the chains. We find that the three-leg ladder can exhibit a spin-gap and/or non-trivial plateaux
in the magnetization curve whose appearance strongly depends on the choice of coupling.
Received 11 February 1999 and Received in final form 16 June 1999 相似文献
5.
Weiqiang Yu Shiping Feng 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(2):265-269
The magnetic properties of the spin liquid state of the antiferromagnetic Heisenberg model on the kagomé lattice are investigated
within the self-consistent mean-field theory. The results show that the spin liquid ground-state energy per site is , which is in very good agreement with the best numerical estimates. The spin structure factor and spin susceptibility are
also discussed.
Received 1 December 1998 and Received in final form 12 April 1999 相似文献
6.
The Thomas-Fermi equation, in conjunction with the Poisson equation is solved exactly for the problem of the two-dimensional
circular parabolic quantum dot in the presence of a weak magnetic field, in the framework of the local spin-density approximation.
The total energy, chemical potential, differential capacitance, degree of polarization, and diamagnetic susceptibility were
calculated. Asymptotic solutions were obtained for the limits of strong and weak confinement.
Received 19 February 1999 and Received in final form 26 July 1999 相似文献
7.
Ll. Serra A. Puente 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(1):77-81
The magnetic extension of the Thomas-Fermi-Weizs?cker kinetic energy is used within density-functional-theory to numerically
obtain the ground state densities and energies of two-dimensional quantum dots. The results are thoroughly compared with the
microscopic Kohn-Sham ones in order to assess the validity of the semiclassical method. Circular as well as deformed systems
are considered.
Received 26 October 2000 and Received in final form 14 December 2000 相似文献
8.
Electronic structures in coupled two quantum dots by 3D-mesh Hartree-Fock-Kohn-Sham calculation 总被引:2,自引:0,他引:2
T. Matsuse T. Hama H. Kaihatsu N. Toyoda T. Takizawa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):391-394
To study the electronic structures of quantum dots in the framework of self-interaction-free including three dimensional effects,
we adopt the theory of nonlocal effective potential introduced by Kohn and Sham [#!ks65!#]. For utilizing the advantageous
point of the real space (3D) mesh method to solve the original nonlinear and nonlocal Hartree-Fock-Kohn-Sham (HFKS)-equation,
we introduce a linearization of the equation in the local form by introducing the local Coulomb potentials which depend on
explicitly the two single particle states. In practice, for solving the local form HFKS-equation, we use the Car-Parrinello-like
relaxation method and the Coulomb potentials are obtained by solving the Poisson equation under proper boundary conditions.
Firstly the observed energy gap between triplet- and singlet-states of N = 4 in DBS [#!tarucha96!#] is discussed to reproduce the addition energies and chemical potentials depending the magnetic
field. Next the coupling between two-quantum dots in TBS [#!aht97!#] is studied by adding the square barrier between two dots.
The spin-degeneracy [#!aht97!#] measured in gate-voltage depending on magnetic field is well reproduced in the limit of small
mismatch. Finally, the electronic states in the ring structure are calculated and discussed how the ring size and magnetic
field affect to the structures.
Received 30 November 2000 相似文献
9.
H. Frahm C. Rödenbeck 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(3):409-414
We study the phase diagram of coupled spin-1/2 chains with bilinear and (chiral) three-spin exchange interactions in a magnetic
field. The model is soluble on a one-parametric line in the space of coupling constants connecting the limiting cases of a
single and two decoupled Heisenberg chains with nearest neighbour exchange only. We give a complete classification of the
low-energy properties of the integrable system and introduce a numerical method which allows to study the possible phases
of spin ladder systems away from the soluble line in a magnetic field.
Received 17 November 1998 and Received in final form 22
January 1999 相似文献
10.
XIEWen-Fang 《理论物理通讯》2001,35(4):497-500
We investigate the effect of the position of the donor in quantum dots on the energy spectrum in the presence of a perpendicular magnetic field by using the method of few-body physics,As a function of the magnetic field,we find,when D^- centers are placed sufficiently off-center,discontinuous ground-state transitions which are similar to those found in many-electron parabolic quantum dots.Series of magic numbers of angular momentum which minimize the ground-state electron-electron interaction energy have been discovered.The dependence of the binding energy of the gound-state of the D^- center on the dot radius for a few values of the magnetic field strength is obtained and compared with other results. 相似文献
11.
Jian-Min Shi V.N. Freire G.A. Farias 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(2):337-348
A theoretical study is performed on the confined electron and shallow donor states properties in graded GaAs/AlxGa1-xAs spherical quantum dots. The two lowest energy levels of a confined electron are obtained taking into account the dependence
of the electron effective mass on the spatial profile of the Al molar fraction. The ground state of a single Si shallow donor,
which may be located at an arbitrary position in the structure, is calculated through a variational approach. Depending on
the dot interface width and localization, we find that the energy levels of the electron and donor states for the system under
study can be blue or red shifted appreciably in comparison to those calculated within the sharp interface picture. We show
that it is necessary to have accurate information concerning the interface of semiconductor dots whose samples are used in
the experiments, in order to achieve a better understanding of their optical properties.
Received 31 May 1999 相似文献
12.
In the asymptotic limit, the interlayer exchange coupling decays as D-2, where D is the spacer thickness. A systematic procedure for calculating the preasymptotic corrections, i.e., the terms of order D-n with ,is presented. The temperature dependence of the preasymptotic corrections is calculated. The results are used to discuss
the preasymptotic corrections for the Co/Cu/Co(001) system.
Received 7 January 1999 相似文献
13.
S. Guérandel T. Badr M.D. Plimmer P. Juncar M.E. Himbert 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(1):33-38
The frequency of the centroid of the transition in Ag I has been determined by laser spectroscopy of a collimated metastable thermal atomic beam. We find MHz. The isotope shift MHz. For the magnetic hyperfine structure constant of the state, assuming IJ coupling, we find, MHz and MHz.
Received 16 July 1999 and Received in final form 7 October 1999 相似文献
14.
15.
B. Pozzi L. Salasnich A. Parola L. Reatto 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(3):367-370
We study the thermodynamics of the Bose-condensed atomic hydrogen confined in the Ioffe-Pritchard potential. Such a trapping
potential, that models the magnetic trap used in recent experiments with hydrogen, is anharmonic and strongly anisotropic.
We calculate the ground-state properties, the condensed and non-condensed fraction and the Bose-Einstein transition temperature.
The thermodynamics of the system is strongly affected by the anharmonicity of this external trap. Finally, we consider the
possibility to detect Josephson-like currents by creating a double-well barrier with a laser beam.
Received 15 February 2000 相似文献
16.
The method of few-body physics is applied to treat a D-<\sup> center quantum dot system in a magnetic field. The magnetic field is applied in the z direction. Using this method, we investigate the energy spectra of low-lying states of D-<\sup> center quantum dots as a function of magnetic field. The dependence of the binding energies of the ground-state of the D-<\sup> center are calculated as a function of the dot radius with a few values of the magnetic field strength and compared with other results. 相似文献
17.
1INTRODUCTIONInrecentyearstherehasbeenmuchexperimentalandtheoreticalinterestinquantumdotsinwhichonlyafewelectronsareboundatse... 相似文献
18.
WANG An-Mei XIE Wen-Fang 《理论物理通讯》2005,44(7)
We study a four-electron system in a vertically coupled four-layer quantum dot under a magnetic field by the exact diagonalization of the Hamiltonian matrix. We find that discontinuous ground-state energy transitions are induced by an external magnetic field. We find that dot-dot distance and electron-electron interaction strongly affect the low-lying states of the coupled quantum dots. The inter-dot correlation leads to some sequences of possible disappearances of ground state transitions, which are present for uncoupled dots. 相似文献
19.
We study a four-electron system in a vertically coupled four-layer quantum
dot under a magnetic field by the exact diagonalization of the Hamiltonian
matrix. We find that discontinuous ground-state energy transitions are induced by an external magnetic field. We find that dot-dot distance and
electron-electron interaction strongly affect the low-lying states of the
coupled quantum dots. The inter-dot correlation leads to some sequences of
possible disappearances of ground state transitions, which are present for
uncoupled dots. 相似文献
20.
The negatively charged exciton in double-layer quantum dots 总被引:1,自引:0,他引:1
Wenfang Xie 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(3):385-389
The hyperangular equation for charged semiconductor complexes in a double-layer harmonic quantum dot was solved numerically
by using the correlated hyperspherical harmonics as basis functions. By using this method, we have calculated the energy spectra
of the low-lying states of a charged exciton as a function of the radius of the quantum dot and the binding energy spectra
of the ground state as a function of the radius of the quantum dot for a few values of the distance between the vertically
coupled dots and the electron-to-hole mass ratio.
Received 3 December 1999 相似文献