抛物量子线中强耦合极化子的有效质量

采用改进的线性组合算符法、Lagrange乘子和变分法,在考虑电子与LO声子相互作用情况下,研究了抛物量子线中强耦合极化子的有效质量和光学声子平均数。通过数值计算,讨论了约束强度ω₀和拉格朗日乘子u对极化子的有效质量m^*和光学声子平均数N及极化子振动频率λ的影响。计算结果表明:有效质量m^*和光学声子平均数N及极化子振动频率λ都随着约束强度ω₀和拉格朗日乘子u的增加而增大。     

晶格热振动对准二维强耦合极化子有效质量的影响

采用Tokuda改变的线性组合算符法和改进的LLP变分法，研究了晶格热振动对无限势垒量子阱中电子与界面光学声子强耦合、与体纵光学声子弱耦合系统的影响，推导出作为阱宽和温度函数的极化子有效质量的表达式. 尤其得到了量子阱中极化子的振动频率及其随阱宽和温度变化的规律. 对KI/AgCl/KI量子阱进行了数值计算，结果表明，极化子的振动频率和有效质量随阱宽的增加而减小、随温度的升高而减小，但不同支声子与电子相互作用对极化子的振动频率和有效质量的贡献以及它们随阱宽和温度的变化情况大不相同. 关键词： 量子阱 强耦合极化子 振动频率 有效质量 温度依赖性     

稳恒电、磁场中量子阱内极化子的基态能量

采用Ｌａｒｓｅｎ谐振子算符代数运算与变分波函数相结合的方法，研究处于与生长轴方向平行的稳恒电、磁场中量子阱内的电子——体纵光学声子相互作用系统。得到系统包括二级微扰修正的、作为量子阶宽度、电子－声子耦合常数以及电、磁场强度函数的基态能量表达式。结果表明：对电子基态能量的极化影响，随阱宽及电场强度的增大而减弱，而随磁场强度的增大而增强。 关键词：     

二维极化子在磁场中的基态能量

谐振子算符的代数运算方法被用于研究磁场中同时与表面光学声子及表面声学声子相互作用的二维电子。得到二维极化子在强磁场中直至四级微扰的基态能量以及它在任意强经磁场中的二级微扰基态能量表达式。结果发现,对磁场中二维极化子基态能量的影响中,表面声学声子有着与表面光学声子同样的甚至更为突出的贡献,是不容忽视的。 关键词：     

极性晶体中与形变势相互作用的表面极化子

有不少的极性晶体,电子与表面光学(SO)声子耦合强,但与表面声学(SA)声子耦合弱.研究电子与SO声子耦合强,与SA声子耦合弱的极性晶体中与形变势相互作用的表面极化子的性质.采用改进了的线性组合算符和微扰法导出了极性晶体中与形变势相互作用的表面极化子的有效哈密顿量.在计及电子在反冲效应中发射和吸收不同波矢的声子之间的相互作用时,讨论对表面极化子的有效哈密顿量、有效质量和有效相互作用势的影响.     

多原子半无限晶体中极化子的激发能量

研究多原子半无限晶体中电子与表面光学SO声子和体纵光学LO声子强耦合的极化子的激发态的性质。采用线性组合算符和幺正变换方法导出强耦合情形下极化子的基态能量、第一内部激发态能量和激发能量。结果表明,多原子半无限晶体中强耦合极化子的基态能量、第一内部激发态能量和激发能量不仅包含不同支LO声子和不同支SO声子与电子耦合的能量,而且还包含不同支LO声子之间和不同支SO声子之间相互作用贡献的附加能量。     

多原子半无限晶体中表面极化子的内部激发态

研究多原子半无限晶体中电子与表面光学(SO)声子耦合强,而与体纵光学(LO)声子耦合弱的极化子的激发态性质.采用线性组合算符和幺正变换方法导出与SO声子耦合强而与LO声子耦合弱情形下极化子的基态能量、第一内部激发态能量和激发能量.结果表明,多原子半无限晶体中与SO声子耦合强,而与LO声子耦合弱的极化子的基态能量、第一内部激发态能量不仅包含不同支LO声子和不同支SO声子与电子耦合的能量,而且也包含不同支SO声子之间相互作用贡献的附加能量.激发能量与体纵光学声子无关.     

量子线中强耦合极化子的温度效应

采用Tokuda改进的线性组合算符法和有效质量下的变分法,研究在抛物势作用下,同时考虑电子与LO声子相互作用时,温度对量子线中强耦合极化子特性的影响。对RbCl晶体所作的数值计算结果表明,量子线中强耦合极化子的基态能量、平均数和光学声子平均数均随温度的升高而增加。     

纤锌矿MgxZn1-xO/Mg0.3Zn0.7O抛物量子阱中极化子能级

采用改进的Lee-Low-Pines(LLP)中间耦合方法研究纤锌矿Mg x Zn1-x O/Mg0.3Zn0.7O抛物量子阱材料中的极化子能级,给出极化子基态能量、跃迁能量(第一激发态到基态)和不同支长波光学声子对电子态能级的贡献随量子阱宽度d的变化规律。理论计算中考虑了纤锌矿Mg x Zn1-x O/Mg0.3Zn0.7O抛物量子阱材料中声子模的各向异性和介电常数、声子(类LO和类TO)频率等随空间坐标Z变化(SD)效应对极化子能量的影响。结果表明,Mg x Zn1-x O/Mg0.3Zn0.7O抛物量子阱中电子与长波光学声子相互作用对极化子能级的移动很大,使得极化子能量明显降低。阱宽较小时,半空间长波光学声子对极化子能量的贡献较大,而定域长波光学声子的贡献较小;阱宽较大时,情况则正好相反。在d的变化范围内,电子与长波光学声子相互作用对极化子能级的移动(约67~79 meV)比Al x Ga1-x As/Al0.3Ga0.7As抛物量子阱中的相应值(约1.8~3.2 meV)大得多。因此,讨论ZnO基量子阱中电子态问题时要考虑电子与长波光学声子的相互作用。     

对称量子阱中极化子的有效质量和自陷能

采用变分微扰法,对量子阱中极化子的有效质量和自陷能进行了研究.考虑到阱对于电子波函数的量子限制效应和界面声子的影响,计算了各支声子与电子相互作用对自陷能的贡献,讨论了极化子的有效质量和自陷能随量子阱宽度的变化关系,进一步说明了量子阱的尺度效应和界面声子作用的重要性. 关键词：     

Diagrammatic weak-coupling expansion for the magneto-polaron energy

The problem of a Pekar-Fröhlich polaron in a magnetic field is considered for weak electron-phonon interaction. A diagrammatic technique for zero temperature is developed. Previously obtained results for two dimensions are reproduced. For three dimensions the polaron ground-state energy and the longitudinal effective mass are derived in the first orders of the electron-phonon coupling constant for non-zero values of a magnetic field. In a strong magnetic field the bulk polaron is shown to be equivalent to a one-dimensional polaron with a renormalized electron-phonon coupling constant. This leads to exact results in the strong-coupling limit.     

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。     

Polaronic effects on the energy levels of a double donor impurity in quantum wells in the presence of a magnetic field

In the presence of a magnetic field the Hamiltonian of the single or double polaron bound to a helium-type donor impurity in semiconductor quantum wells (QWs) are given in the case of positively charged donor center and neutral donor center. The couplings of an electron and the impurity with various phonon modes are considered. The binding energy of the single and double bound polaron in Al_xlGa _1-xlAs/GaAs/Al_xrGa _1-xrAs QWs are calculated. The results show that for a thin well the cumulative effects of the electron-phonon coupling and the impurity-phonon coupling can contribute appreciably to the binding energy in the case of ionized donor. In the case of neutral donor the contribution of polaronic effects are not very important, however the magnetic field significantly modifies the binding energy of the double donor. The comparison between the binding energies in the case of the impurity placed at the quantum well center and at the quantum well edge is also given. Received 16 February 1999     

表面极化子光学声子平均数的磁场和温度依赖性

采用变分法、幺正变换和拉格朗日乘子法,研究了有限温度下纯二维晶体中表面磁极化子的性质.讨论了表面光学声子平均数、磁极化子振动频率λ与磁场B、温度T及Lsgrange乘子u之间的关系.对KCl晶体进行了数值计算,结果表明:磁极化子振动频率、表面光学声子平均数均随磁场B的增强而增加,且随温度T升高而增加.当bgrange乘子u超出慢电子范围时磁极化子振动频率、表面光学声子平均数均随u增加而增大且变化越来越显著.     

Magnetic-field effects on exciton–polaron in a CdSe quantum disk

We study theoretically the interaction between excitons and longitudinal optical (LO) phonons in a cylindrical disk-like semiconductor quantum dot under an applied magnetic field. Due to the intensity of the interaction in the strong coupling regime, a composite quasi-particle called exciton–polaron is formed. We focus on the effect of the disk size and an external magnetic field on the exciton–phonon interaction energy and the exciton–polaron modes. The numerical computation for a CdSe quantum disk have shown that the exciton–phonon interaction energy is very significant and is even dominant when the disk height is small, which leads to a large Rabi splitting between the exciton–polaron modes. We investigate also the effect of the temperature on the integrated photoluminescence (PL) intensity, and show that at relatively high temperature the LO phonons have a noticeable effect on it. This physical parameter also shows a great dependence on quantum disk size and on magnetic field.     

STRONG-COUPLING SURFACE OPTICAL POLARON IN A MAGNETIC FIELD

A variational scheme of the Pekar type is employed to study the strong-coupling optical polaron on the outer surface of the polar crystal under the influence of a magnetic field. The ground state energy and the effective mass of the polaron are obtained as functions of the magnetic field strength and the electron-surface optical phonon coupling constant. It is shown that the effective mass of the surface polaron appears in nonisotropic nature due to the coupling between the electron and the surface optical phonon.     

Properties of a Bound Polaron under a Perpendicular Magnetic Field

We investigate the influence of a perpendicular magnetic field on a bound polaron near the interface of a polar-polar semiconductor with Rashba effect. The external magnetic field strongly changes the ground state binding energy of the polaron and the Rashba spin-orbit （SO） interaction originating from the inversion asymmetry in the heterostructure splits the ground state binding energy of the bound polaron. In this paper, we have shown how the ground state binding energy will be with the change of the external magnetic field, the location of a single impurity, the wave vector of the electron and the electron areal density, taking into account the SO coupling. Due to the presence of the phonons, whose energy gives negative contribution to the polaron＇s, the spin-splitting states of the bound polaron are more stable, and we find that in the condition of week magnetic field, the Zeeaman effect can be neglected.     

强耦合表面极化子的激发能量

采用线性组合算符方法及幺正变换方法研究了电子与表面光学(SO)声子和体纵光学(LO)声子均为强耦合的表面极化子的激发态性质.计算了体系的有效哈密顿量、振动频率和体系由基态向第一激发态跃迁所需的激发能量.     

Adiabatic approximation for a bound acoustic deformation potential polaron in a strong magnetic field

On the basis of the usual adiabatic scheme applied to a bound polaron in a strong magnetic field we observe an enhancement of the binding energy due to electron-lattice coupling via the deformation potential. This enhancement, being more pronounced with increasing field intensity, is, however, negligible for most common materials in experimentally interesting magnetic fields.     

耦合强度和磁场对极化子基态的影响

利用线性组合算符和幺正变换相结合的方法,推导出极化子基态与耦合强度和磁场强度的关系。数值计算表明:当磁场强度给定时,随着耦合常数α的增加,振动频率λ先减小后增大;基态能量E₀单调下降;自陷能E_0tr单调增大;Landau能E_0L先增大,达到最大值后又下降。当耦合强度给定时,随着磁场强度的增大,λ单调增大,且α愈小,λ增加愈快;基态能量E₀随磁场强度的增大而增大;自陷能E_0tr随着磁场强度的增大而略有增加;Landau能E_0L随着磁场强度的增大先增大,达到最大值后,又开始下降。