共查询到20条相似文献,搜索用时 15 毫秒
1.
The problem of bound polarons in quantum dot quantum well (QDQW)
structures is studied theoretically. The eigenfrequencies of bulk
longitudinal optical (LO) and surface optical (SO) modes are derived
in the framework of the dielectric continuum approximation. The
electron--phonon interaction Hamiltonian for QDQW structures is
obtained and the exchange interaction between impurity and
LO-phonons is discussed. The binding energy and the trapping energy
of the bound polaron in CdS/HgS QDQW structures are calculated. The
numerical results reveal that there exist three branches of
eigenfrequencies of surface optical vibration in the CdS/HgS QDQW
structure. It is also shown that the binding energy and the trapping
energy increase as the inner radius of the QDQW structure decreases,
with the outer radius fixed, and the trapping energy takes a major
part of the binding energy when the inner radius is very small. 相似文献
2.
This paper reports that the ground-state energy of polaron was obtained with strong electron-LO-phonon coupling by using a variational method of the Pekar type in a parabolic quantum dot. Quantum transition is occurred in the quantum system due to the electron-phonon interaction and the influence of temperature. That is the polaron transit from the ground-state to the first-excited state after absorbing a LO-phonon and it causes the change of the polaron lifetime. Numerical calculations are performed and the results illustrate that the ground-state lifetime of the polaron will increase with increasing the ground-state energy of polaron and decrease with increasing the electron-LO-phonon coupling strength, the confinement length of the quantum dot and the temperature. 相似文献
3.
采用求解能量本征方程、LLP幺正变换、变分相结合的方法研究 球壳量子点中极化子和量子比特的声子效应. 数值计算表明: 声子效应使极化子的基态(或激发态)能量小于电子的基态(或激发态)能量, 使量子比特的振荡周期减小, 且内径给定时, 随着外径的增大声子效应对极化子和量子比特振荡周期的影响越大; 声子效应不改变量子比特内电子概率密度分布的幅值, 量子比特内中心球面处概率密度幅值最大, 界面处概率密度为零, 其它处的概率密度幅值介于最大和最小之间, 且各个空间点的概率密度随半径和方位角的变化而变化, 随时间做周期性振荡. 相似文献
4.
A variational approach is used to study the ground state of a bound polaron in a spherical quantum dot under an external electric field. The binding energy of the hydrogenic impurity state is calculated by taking the interaction of an electron with both the confined longitudinal optical phonons and the surface optical phonons into account. The interaction between impurity and longitudinal optical phonons has also been considered to obtain the binding energy of a bound polaron. It shows that the polaron effects give significant corrections to the binding energy and its Stark energy shift. The external electric field increases the phonon contributions to the binding energy. 相似文献
5.
6.
S.A. Safwan A.S. Asmaa Nagwa El meshed M.H. Hekmat TH.M. El-Sherbini S.H. Allam 《Superlattices and Microstructures》2010
Within the effective mass approximation, we investigated theoretically the ground-state energy of a single particle and the binding energy of the neutral donor impurity (D0) affected by a lateral electric field in a parabolic quantum dot (QD). The results show that the electron and the hole ground-state energy and the band to band transition energies shift to lower values (red shift) by increasing the field intensity. The quantum Stark shift (QSS) for the electron increases rapidly in the quasi spherical QD (QSQD) by increasing the lateral field, whereas for the hole it increases monotony. In the cylindrical QDs (CQDs), we found that the QSS for electron and hole increase monotonically. The quantum size, lateral electric field and impurity position effect on the binding energy of neutral donor (D0) is studied. Unexpected behavior of D0 in quantum well limit (QW), the binding energy of D0 is increasing (blue shift) with increasing QD radius R at the presence of a lateral electric field. It appears that for a fixed size of the QD, the off-center binding energy decreases when the impurity ion is displaced from the center to the QD borders, while it is shifted to lower energy with increasing the field. 相似文献
7.
This paper calculates the time evolution of the quantum mechanical
state of an electron by using variational method of Pekar type on
the condition of electric--LO-phonon strong coupling in a parabolic
quantum dot. It obtains the eigenenergies of the ground state and
the first-excited state, the eigenfunctions of the ground state and
the first-excited state This system in a quantum dot may be employed
as a two-level quantum system qubit. The superposition state
electron density oscillates in the quantum dot with a period when
the electron is in the superposition state of the ground and the
first-excited state. It studies the influence of the electric field
on the eigenenergies of the ground state, the first-excited state
and the period of oscillation at the different electron--LO-phonon
coupling constant and the different confinement length. 相似文献
8.
This paper presents the influence of Rashba effect on bound magnetopolaron in delta quantum dot. The unitary transformation method and the variational method of Pekar type have been used to derive the ground and first excited state energy. Due to Rashba effect, the ground and first excited states each split into two energies (spin up and down). Results show that the split up(down) energy of ground and first excited states are increasing (decreasing) function of wave vector; the spin splitting of the ground and first excited states are decreasing function of the delta parameter and the increasing function of Rashba parameter. It has also be seen that the splitting of energies levels occur around the value . The density of probability has its minimum value at the center of the dot while it is maximal at the boundary of the dot. The decoherence has been studied through the Shannon entropy and the results show increase of entropy with time, delta parameter K, and cyclotron frequency ωc. It also suggests a way to encrypt information and to control decoherence. 相似文献
9.
We study the eigenenergies and eigenfunctions of the
ground and first-excited states of an electron which is
strongly coupled to an LO-phonon in a quantum dot with a triangular
bound potential and Coulomb bound potential by using the Pekar
variational method. This system may be used as a two-level qubit.
Phonon spontaneous emission causes the decoherence of the qubit.
Numerical calculations are performed on the decoherence rate as a
function of the polar angle, the Coulomb binding parameter, the
coupling strength, the confinement length of the quantum dot and the
dispersion coefficient. 相似文献
10.
Shi-Hua Chen Jing-Lin Xiao 《Physica E: Low-dimensional Systems and Nanostructures》2008,40(9):2941-2944
A Landau–Pekar variational theory is employed to obtain the ground and the first excited state binding energies of an electron bound to a Coulomb impurity in a polar semiconductor quantum dot (QD) with parabolic confinement in both two and three dimensions. It is found that the binding energy increase with increasing the Coulomb binding parameter and increase with the decrease in size of the QD and is much more pronounced with decreasing dimensionality. 相似文献
11.
Magnetpolaron effect in two-dimensional anisotropic parabolic quantum dot in a perpendicular magnetic field 下载免费PDF全文
We study the two-dimensional weak-coupling Fr o¨hlich polaron in a completely anisotropic quantum dot in a perpendicular magnetic field. By performing a unitary transformation, we first transform the Hamiltonian into a new one which describes an anisotropic harmonic oscillator with new mass and trapping frequencies interacting with the same phonon bath but with different interaction form and strength. Then employing the second-order Rayleigh–Schr o¨dinger perturbation theory, we obtain the polaron correction to the ground-state energy. The magnetic field and anisotropic effects on the polaron correction to the ground-state energy are discussed. 相似文献
12.
The polaron effect on the optical rectification in spherical quantum dots with a shallow hydrogenic impurity in the presence of electric field is theoretically investigated by taking into account the interactions of the electrons with both confined and surface optical phonons. Besides, the interaction between impurity and phonons is also considered. Numerical calculations are presented for typical Zn_(1-x)Cd_xSe/ZnSe material. It is found that the polaronic effect or electric field leads to the redshifted resonant peaks of the optical rectification coefficients. It is also found that the peak values of the optical rectification coefficients with the polaronic effect are larger than without the polaronic effect, especially for smaller Cd concentrations or stronger electric field. 相似文献
13.
Shi-Hua Chen 《Physica B: Condensed Matter》2011,406(10):2033-2037
A variational approach is employed to obtain the ground and the first excited state binding energies of an electron bound to a hydrogenic impurity in a polar semiconductor quantum dot (QD) with symmetric parabolic confinement in both two and three-dimensions. We perform calculations for the entire range of the electron-phonon coupling constant and the Coulomb binding parameter and for arbitrary confinement length. It is found that the binding energy of ground and first excited state is larger in a two-dimension (2D) dot than in a three-dimension (3D) dot and this trend is more pronounced with the increase of the electron-phonon coupling constant for the same value of the Coulomb binding parameter and confinement length. Furthermore, the ground and the first excited state binding energy increases with increasing the Coulomb binding parameter in both 2D and 3D QDs for the same electron-phonon coupling constant. 相似文献
14.
The energy levels of a polaron in a wurtzite nitride finite parabolic quantum well (PQW)are studied by a modified Lee-Low-Pines variational method. The ground state of the polaron, the transition energy from first exited state to the ground state and the
关键词:
氮化物抛物量子阱
电子-声子相互作用
极化子 相似文献
15.
16.
A variational approach is presented for calculating the ground-state (GS) binding energies of an electron bound to a Coulomb impurity in a polar semiconductor quantum dot (QD) with parabolic confinement in both two and three dimensions. We perform calculations for the entire range of the electron-phonon coupling constant and the Coulomb binding parameter and for arbitrary confinement length. It is found that the polaronic effect is stronger in a two dimensions (2D) dot than in a three dimensions (3D) dot and this trend is more pronounced with the increase of the coupling constant. Furthermore, the GS binding energy increases with increasing the Coulomb binding parameter in both 2D and 3D QDs for the same electron–phonon coupling constant. The results also indicate that this effect becomes much more pronounced with decreasing dimensionality. 相似文献
17.
本文以含有类氢杂质的三角束缚势量子点为基础,应用Pekar变分方法,电子与体纵光学声子强耦合的条件下得出了电子的基态和第一激发态的本征能量及基态和第一激发态的波函数,量子点中这样的二能级体系可作为一个量子比特.讨论了能量与库仑结合参数,耦合强度,受限长度以及极角的变化关系. 相似文献
18.
用改进的Lee-Low-Pines变分方法研究纤锌矿In0.19Ga0.81N/GaN量子阱结构中束缚极化子能量和结合能等问题,给出基态结合能、不同支长波光学声子对能量和结合能的贡献随阱宽和杂质中心位置变化的数值结果.在数值计算中包括了该体系中声子频率的各向异性和内建电场对能量和结合能的影响、以及电子和杂质中心与长波光学声子的相互作用.研究结果表明,In0.19Ga0.81N/GaN量子阱材料中光学声子和内建电场对束缚极化子能量和结合能的贡献很大,它们都引起能量和结合能降低.结合能随着阱宽的增大而单调减小,窄阱中减小的速度快,而宽阱中减小的速度慢.不同支声子对能量和结合能的贡献随着阱宽的变化规律不同.没有内建电场时,窄阱中,定域声子贡献小于界面和半空间声子贡献,而宽阱中,定域声子贡献大于界面和半空间声子贡献.有内建电场时,定域声子贡献变小,而界面和半空间声子贡献变大,声子总贡献也有明显变化.在In0.19Ga0.81N/GaN量子阱中,光学声子对束缚极化子能量和结合能的贡献比GaAs/Al0.19Ga0.81As量子阱中的相应贡献(约3.2—1.8和1.6—0.3 meV)约大一个数量级.阱宽(d=8 nm)不变时,在In0.19Ga0.81N/GaN量子阱中结合能随着杂质中心位置Z0的变大而减小,并减小的速度变快.随着Z0的增大,界面和半空间光学声子对结合能的贡献缓慢减小,而定域光学声子的贡献缓慢增大. 相似文献
19.
20.
Yi-Ming Liu 《中国物理 B》2022,31(5):57201-057201
New characteristics of the Kondo effect, arising from spin chirality induced by the Berry phase in the equilibrium state, are investigated. The analysis is based on the hierarchical equations of motion (HEOM) approach in a triangular triple quantum-dot (TTQD) structure. In the absence of magnetic field, TTQD has four-fold degenerate chiral ground states with degenerate spin chirality. When a perpendicular magnetic field is applied, the chiral interaction is induced by the magnetic flux threading through TTQD and the four-fold degenerate states split into two chiral state pairs. The chiral excited states manifest as chiral splitting of the Kondo peak in the spectral function. The theoretical analysis is confirmed by the numerical computations. Furthermore, under a Zeeman magnetic field B, the chiral Kondo peak splits into four peaks, owing to the splitting of spin freedom. The influence of spin chirality on the Kondo effect signifies an important role of the phase factor. This work provides insight into the quantum transport of strongly correlated electronic systems. 相似文献