Rashba effect of the bound magnetopolaron in an asymmetry quantum well

Using Pekar variational method, we studied the Rashba effect of the bound magnetopolaron in an asymmetry quantum well. The expression of the ground state energy of the bound magnetopolaron is obtained by theoretical derivation. Due to the influence of the Rashba effect, the ground state energy of the bound magnetopolaron splits into two branches. This phenomenon fully demonstrates that the influence of orbit and spin interaction in different directions on the energy of the polaron is not negligible. Because the contribution of the magnetic field cyclotron resonance frequency to the Rashba spin–orbit splitting is a positive value, the energy spacing becomes larger as the magnetic field cyclotron resonance frequency increases. Due to the presence of impurities, the polaron is more stable than the bare electron state, and the energy splitting is more stable.     

Bound polaron in a quantum pseudodot under Rashba effect

In the present work, the influence of Rashba effect on bound polaron in a quantum pseudodot is studied. Using the Lee–Low–Pines unitary transformation method and the Pekar type variational procedure, we have derived an expression for the bound polaron ground state energy. The ground state energy as functions of the wave vector, the electron–phonon coupling strength, and quantum confinement size is obtained by considering different Coulomb bound potentials. It is found that (i) the ground state energy is decreased with raising the Coulomb bound potential, the electron–phonon coupling strength, and quantum confinement size. (ii) The ground state energy increases when the wave vector is increasing. (iii) The ground state energy splits into two branches (spin-up and spin-down) due to the Rashba effect.     

Polaronic Effects on the Impurity Binding Energy in a Polar Crystal Slab Within an Electric Field

The effects of the interaction between electron and bulk longitudinal optical (LO) phonon and surface optical (SO) phonon on the impurity binding energy of the ground state in a polar crystal slab within an external electric field are derived by using the method of a variational wavefunction. The binding energy of the bound polaron is obtained as a function of the impurity position, the slab thickness and the electric field strength. It is found that the polaronic correction to the impurity binding energy by the SO phonon may be enhanced and that by the LO phonon may be reduced with increasing electric field strength. And the effect of the electron-phonon interaction is quite important in increasing the values of binding energy.     

Bound polaron in a spherical quantum dot under an electric field

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.     

抛物量子点中强耦合束缚磁极化子的声子平均数

采用线性组合算符和幺正变换方法导出了强耦合束缚磁极化子的振动频率和声子平均数。讨论了量子点的有效受限长度、磁场、库仑场和电子-LO声子耦合强度对抛物量子点中强耦合束缚磁极化子振动频率和声子平均数的影响。数值计算结果表明:强耦合束缚磁极化子的振动频率和声子平均数均随量子点的有效受限长度、回旋共振频率的增加而减小,随库仑束缚势的增加而增加,声子平均数随电子-LO声子耦合强度增加而减小。     

Rashba效应影响下量子点中弱耦合束缚极化子的性质

采用改进的线性组合算符和幺正变换的方法研究了Rashba效应影响下量子点中弱耦合束缚极化子的性质,导出了Rashba效应影响下量子点中弱耦合束缚极化子的振动频率、有效质量、基态分裂能和相互作用能。数值计算结果表明随Rashba自旋-轨道耦合常数的增加,由于声子作用产生的附加能量能对零磁场时自旋分裂能的影响占有绝对优势。库仑势对束缚极化子的基态能量的影响同时也占有绝对优势。所以,研究Rashba自旋轨道相互作时声子的影响不可忽略。     

Rashba效应影响下量子点中弱耦合束缚极化子的性质

采用改进的线性组合算符和幺正变换的方法研究了Rashba效应影响下量子点中弱耦合束缚极化子的性质,导出了Rashba效应影响下量子点中弱耦合束缚极化子的振动频率、有效质量、基态分裂能和相互作用能。数值计算结果表明随Rashba自旋-轨道耦合常数的增加,由于声子作用产生的附加能量能对零磁场时自旋分裂能的影响占有绝对优势。库仑势对束缚极化子的基态能量的影响同时也占有绝对优势。所以,研究Rashba自旋轨道相互作时声子的影响不可忽略。     

抛物量子点中强耦合束缚极化子的光学声子平均数

采用线性组合算符和幺正变换方法研究了在库仑场束缚下抛物量子点中强耦合束缚极化子的振动频率和光学声子平均数,并对其进行了数值计算。结果表明:强耦合束缚极化子的振动频率和光学声子平均数随量子点的有效受限长度的增加而减小,随电子-LO声子耦合强度的增强而增加,束缚极化子的振动频率随库仑势的增加而减小。     

Singularities of the magnetization of a two-dimensional diluted magnetic semiconductor with strong spin-orbit interaction

The properties of the bound states of magnetic impurities and localized carriers in two-dimensional semiconductor systems with strong Rashba spin-orbit interaction have been investigated. The peculiar behavior of the bound states of an electron in such a system leads to the dependence of the ground state of polarons on the external magnetic field. This results in a jump in the dependence of the magnetization on the applied field.     

光学极化子性质对耦合强度和磁场的依赖性

应用线性组合算符和幺正变换方法,研究磁场和耦合强度对光学极化子性质的影响。数值计算表明:当电子接近晶体表面时,光学极化子的振动频率、基态能量和第一激发能仅与磁场有关,且随磁场强度的增强而增大;当电子远离晶体表面时,基态能量和第一激发能与磁场强度和耦合参数均有关,且随磁场强度和耦合参数的增加而增加。     

Rashba效应对抛物量子阱中极化子基态能的影响

采用LLP变分法研究了抛物量子阱中极化子的Rashba效应,得到了极化子基态能量的表达式,并讨论了半阱宽及波矢与基态能量之间的关系.结果显示,基态能量是半阱宽和电子-声子耦合强度的减函数,而是波矢的增函数.由于Rashba效应基态能量零自旋轨道分裂成两支.     

弱耦合多原子半无限晶体中磁极化子的激发能量

近年来国内外对多原子极性晶体中磁极化子性质的研究十分活跃,Zorkani等采用变分法计算了束缚磁极化子的基态能量,Kandemir等采用束缚朗道态讨论了二维大磁极化子的基态和第一激发态能量,国内一些学者采用微扰法和新颖算符法讨论了多原子极性晶体中表面和体磁极化子的性质。采用线性组合算符和幺正变换,研究磁场中多原子半无限极性晶体中电子和光学声子弱耦合相互作用所产生的极化子的第一激发态能量及平均声子数。结果表明:当电子无限接近晶体表面时,磁极化子的基态能量仅为Landau能量;第一激发态能量为Landau基态能量的2倍;平均声子数等于各支与电子耦合的体光学声子数和表面光学声子数之和。而当电子处于晶体深处时,磁极化子的基态能量却为Landau基态能量与各支体光学声子以及表面光学声子分别耦合的能量之和;第一激发态能量仍为Landau基态能量的2倍;平均声子数等于各支与电子耦合的体光学声子数和与所处深度有关的各支体光学声子数之和,而与各支表面光学声子无关。     

束缚磁极化子的性质

采用线性组合算符和幺正变换方法分别导出弱、强耦合情形下束缚磁极化子的振动频率和基态能量.结果表明库仑场的存在使得磁极化子的基态能量的绝对值变小.     

抛物量子阱中束缚极化子的极化势和结合能

利用改进的Lee-Low-Pines(LLP)方法,用变分法计算了无限深抛物量子阱中同时考虑与体纵光学声子和界面纵光学声子相互作用的束缚极化子的极化势和结合能.数值计算得出:阱宽较大时极化势很小,阱宽较小时极化势较大,所以对于较窄的抛物阱必须考虑极化势.对于给定阱宽的抛物阱,随着远离阱中心极化势迅速减小,当到达阱的界面附近极化势又开始增大.阱宽较小时,束缚极化子的结合能随着阱宽L的增大而急剧减小;阱宽较大时,结合能减小的非常缓慢,最后接近体材料中的三维值.     

On lower bound estimates for the energy spectrum of the Fr?hlich polaron model

Method of intermediate problems was applied to investigation of the energy spectrum of the Fr?hlich polaron model. It was shown that various infinite sequences of non-decreasing improvable lower bound estimates for the low-lying branch of the slow-moving polaron excitation energy spectral curve adjacent to the ground state energy can be derived for arbitrary values of the electron-phonon interaction constant. These bound estimates allow for explicit numerical evaluation at all orders. In conjunction with numerous well-known upper bound estimates for the energy spectral curve of the Fr?hlich polaron as a function of the interaction constant and the polaron total momentum, the aforesaid improvable lower bound estimates might provide one with virtually precise magnitude for the energy of the slow-moving polaron. Possible generalization to the case of the Fr?hlich polaron in external magnetic field is outlined.     

Bound polaron in a wurtzite GaN/AlxGa1 − xN ellipsoidal finite-potential quantum dot

A variational method is used to study the ground state of a bound polaron in a weakly oblate wurtzite GaN/Al_xGa_1 − xN ellipsoidal quantum dot. The binding energy of the bound polaron is calculated by taking the electron couples with both branches of LO-like and TO-like phonons due to the anisotropic effect into account. The interaction between impurity and phonons has also been considered to obtain the binding energy of a bound polaron. The results show that the binding energy of bound polaron reaches a peak value as the quantum dot radius increases and then diminishes for the finite potential well. We found that the binding energy of bound polaron is reduced by the phonons effect on the impurity states, the contribution of LO-like phonon to the binding energy is dominant, the anisotropic angle and ellipticity influence on the binding energy are small.     

氮化物抛物量子阱中磁极化子的能量

利用改进的Lee-Low-Pines(LLP)方法和变分法研究了在外磁场作用下氮化物无限抛物量子阱中自由极化子的能级,得到了极化子基态能量随量子阱阱宽和外磁场变化的规律,对GaN/Al_0.3Ga_0.7N抛物量子阱进行了数值计算.结果表明:外磁场对极化子的能量有明显的影响,极化子基态能量随阱宽的增强而减小,随磁场的增强而增大,并且电子-声子相互作用对氮化物量子阱中极化子能量的贡献是很大的.     

外电场作用下纤锌矿氮化物抛物量子阱中极化子能级

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     

库仑场对抛物量子点中强耦合极化子性质的影响

采用线性组合算符和幺正变换方法研究了在库仑场束缚下抛物量子点中强耦合束缚极化子的振动频率和基态能量。并对其进行了数值计算,结果表明:强耦合束缚极化子的振动频率和基态能量随量子点的有效受限长度的增加而减小,随电子-LO声子耦合强度的增加而增加,束缚极化子的基态能量随库仑势的增加而减小。     

声子和磁场对量子环中极化子性质的影响

采用求解能量本征方程、幺正变换和变分相结合的方法,研究声子和磁场对量子环中极化子性质的影响. 对KBr量子环的数值计算表明,电子或极化子的基态能量随量子环频率(或平均半径)的增大而增大,极化子基态能移随量子环频率的增大(或平均半径的减小)而减小,极化子中的平均声子数随量子环频率的增大(或平均半径的减小)而增大. 当有垂直磁场时,极化子基态能量和基态能移与外磁场及电子转动状态有关. 随着磁场强度的增大,基态能量出现简并且呈现非周期性振荡;能移随磁场强度的增大(或转动量子数绝对值的减小)而减小.