Two Interacting Electrons in a Vertically Coupled Quantum Dot

We study a two-electron system in a double-layer quantum dot under a magnetic field by means of the exact diagonalization of the Hamiltonian matrix.We find that discontinuous ground-state energy transitions are induced by an external magnetic field in the case of strong coupling.However,in the case of weak coupling,the angular momentum L of the true ground state does not change in accordance with the change of the magnetic field B and remains L=0.     

Two Interacting Electrons in a Spherical Gaussian Confining Potential Quantum Well

Two-electron states of a three-dimensional spherical GaAs quantum dot (QD) with a Gaussian confining potential confinement are studied. Calculations are made by using the method of few-body physics within the effectivemass approximation. We have calculated the energy levels of single and triplet states as functions of the range and depth of the confining potential well in the spherical QDs. The same calculations performed with the parabolic approximation of the Gaussian potential lead to the results, which are qualitatively and quantitatively different.     

Energy Spectra of Three-Electron Quantum Dots

By making use of the method of few-body physics, the energy spectra of three electrons confined by two-dimensional and three-dimensional quantum dots (QDs) are investigated. Using the present results, the size and shape effects of QDs on the spectra are revealed.     

Effect of the Electron—Phonon Coupling on Barrier D^— Quantum Dots in Magnetic Fields

The influence of the electron-phonon coupling of the energy of low-lying states of the barrier D^- center,which consists of a positive ion located on the z-azis at a distance from the two-dimensional quantum dot plane and two electrons in the dot plane bound by the ion,is investigated at arbitrary strength of maguetic field by mading use of the method of few-body physics.Discontinuous ground-state energy transitions induced by the magnetic field are reported.The dependence of the binding energy of the D^- ground state on the quantum dot radius is obtained.A considerable enhancement of the binding is found for the D^- ground state,which results from the confinement of electrons and electron-phonon coupling.     

Binding Energy of an Exciton Bound to Ionized Acceptor in Quantum Dots

Binding energiesfor an exciton (X ) trapped in the two-dimensional quantum dot by a negative ion located on the z axis at a distance from the dot plane are calculated by using the method of few-body physics.This configuration is called a barrier (A-,X) center.The dependence of the binding energy of the ground state of the barrier (A-,X)center on the electron-to-hole mass ratio for a few values of the distance d between the fixed negative ion on the z axis and the dot plane is obtained.We find that when d → 0,the barrier (A-,X) center has not any bound state.We also studied the stability and binding energy of the ground state of the barrier (A-,X) center in a parabolic quantum dot as a function of the distance d between the fixed negative ion on the z axis and the dot plane.``     

Binding Energy of an Exciton Bound to Ionized Acceptor in Quantum Dots

Binding energiesfor an exciton (X) trapped in the two-dimensional quantum dot by a negative ion located on the z axis at a distance from the dot plane are calculated by using the method of few-body physics.This configuration is called a barrier (A^-,X) center.The dependence of the binding energy of the ground state of the barrier (A^-,X)center on the electron-to-hole mass ratio for a few values of the distance d between the fixed negative ion on the z axis and the dot plane is obtained.We find that when d → 0,the barrier (A^-,X) center has not any bound state.We also studied the stability and binding energy of the ground state of the barrier (A^-,X) center in a parabolic quantum dot as a function of the distance d between the fixed negative ion on the z axis and the dot plane.     

Charged-Exciton Complexes in Quantum Dots

It is known experimentally that stable charged-exciton complexes can exist in low-dimensional semiconductor nanostructures. Much less is known about the properties of such charged-exciton complexes since three-body problems are very difficult to be solved, even numerically. Here we introduce the correlated hyperspherical harmonics as basis functions to solve the hyperangular equation for negatively and positively charged excitons (trions) in a harmonic quantum dot. 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 quantum dot. Based on symmetry analysis, the level crossover as the dot radius increases can be fully explained as the results of symmetry constraint.``     

The Electron-Hole Pair in a Single Quantum Dot and That in a Vertically Coupled Quantum Dot

The energy spectra of low-lying states of an exciton in a single and a vertically coupled quantum dots arestudied under the influence of a perpendicularly applied magnetic field. Calculations are made by using the method ofnumerical diagonalization of the Hamiltonian within the effective-mass approximation. We also calculated the bindingenergy of the ground and the excited states of an exciton in a single quantum dot and that in a vertically coupledquantum dot as a function of the dot radius for different values of the distance and the magnetic field strength.     

Charged-Exciton Complexes in Quantum Dots

It is known experimentally that stable charged-exciton complexes can exist in low-dimensional semiconductor nanostructures. Much less is known about the properties of such charged-exciton complexes since three-body problems are very difficult to be solved, even numerically. Here we introduce the correlated hyperspherical harmonics as basis functions to solve the hyperangular equation for negatively and positively charged excitons (trions) in a harmonic quantum dot. 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 quantum dot. Based on symmetry analysis, the level crossover as the dot radius increases can be fully explained as the results of symmetry constraint.     

Magic Numbers and Ground-State Transitions of Coupled Quantum Dots

The methods for few-body physics are introduced to extract features of a double dot contained three electrons. We find that the electron correlation in double dot leads to angular momentum magic numbers being distinct from those of a single dot. Discontinuous groundstate transitions induced by an external magnetic field have been predicted. The decisive effect of symmetry has been emphasized.     

The Electron－Hole Pair in a Single Quantum Dot and That in a Vertically Coupled Quantum Dot

The energy spectra of low-lying states of an exciton in a single and a vertically coupled quantum dots are studied under the influence of a perpendicularly applied magnetic field. Calculations are made by using the method of numerical diagonalization of the Hamiltonian within the effective-mass approximation. We also calculated the binding energy of the ground and the excited states of an exciton in a single quantum dot and that in a vertically coupled quantum dot as a function of the dot radius for different vaJues of the distance and the magnetic field strength.     

Four-Electron Systems in a Coupled Double-Layer Quantum Dots

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.     

Two-Electron Energy Spectrum in a Parabolic Quantum Dot Under a Magnetic Field

Two interacting electrons in a harmonic oscillator potential under the influence of a perpendicular homo-geneous magnetic field are considered. The energies of two-electron quantum dots with the electron-LO-phonon couplingas a function of magnetic field are calculated. Calculations are made by using the method of few-body physics withinthe effective-mass approximation. Our results show that the electron-LO-phonon coupling effect is very important insemiconductor quantum dots.     

Off—Center D—Centers in a Quantum Dot in the Presence of a Perpendicular Magnetic Fields

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.     

The Spectra of Low-Lying States of Three-Dimensional Quantum Dots in a Magnetic Field

We have studied three-electron systems in three-dimensional anisotropic parabolic quantum dots with the cylindrical symmetry in magnetic fields by means of the method of few-body physics. The results show that the energy levels of a number of states are the lowest, as the magic angular momentum states of two-dimensional quantum dots.     

量子点中磁激子的极化子效应

采用推广的LLP方法研究了自组织量子点中磁激子的极化子效应。考虑带电粒子和声子的相互作用,得到了激子能量随磁场的变化关系。结果表明,激子-声子的相互作用降低了激子的能量,但影响很小;极化子效应在没有外磁场时较明显,随着外磁场的增加,这种效应变得越来越弱。     

Two Electrons with Spin-Orbit Interactions in InAs Coupled Quantum Dots

We theoretically study the spin properties of two interacting electrons confined in the IhAs parallel coupled quantum dots （CQDs） with spin-orbit interactions （SOI） by exact diagonalization method. Through the SOI induced spin mixing of the singlet and the triplet states, we show the different spin properties for the weak and strong SOI. We investigate the coherent singlet-triplet spin oscillations of the two electrons under the SOI, and demonstrate the detailed behaviors of the spin oscillations depending on the SOI strengths, the inter-dot separations and the external magnetic fields. To better understand the underlying physics of the spin dynamics, we introduce a four-level model Hamiltonian for both weak and strong SOI, and find that the SOI induced in plane effective magnetic fields can be quantitatively extracted from the two-electron excitation energy spectra.     

Positively Charged Exciton in Double-Layer Quantum Dots

The Hamiltonian equation for positively charged exciton in double-layer harmonic quantum dots is solved numerically by using the exact diagonalization techniques. We find that the correlation energy Ec of positively charged exciton increases with increasing the confinement strength and the binding energy decreases obviously for the heavy hole.     

Positively Charged Exciton in Double-Layer Quantum Dots

The Hamiltonian equation for positively charged exciton in double-layer harmonic quantum dots is solved numerically by using the exact diagonalization techniques. We find that the correlation energy Ec of positively charged exciton increases with increasing the confinement strength and the binding energy decreases obviously for the heavy hole.     

Linear and Nonlinear Optical Properties in Spherical Quantum Dots

We calculate the energy eigenvalues and the sate functions of one-electron Quantum Dot （QD） by using a combination of Quantum Genetic Algorithm （QGA） and Hartre-Fock-Roothaan （HFR） method. The linear and the third-order nonlinear optical absorption coefficients for the 1s-1p, 1p-1d, and 1d-1f transitions are examined as a function of the incident photon energy for three different values of the stoichiometric ratio. The results show that the stoichiometric ratio, impurity, relaxation time, and dot size have great influence on the optical absorption coefficients of QDs.