磁场和抛物势对半指数量子阱极化子振动频率的影响

量子阱由于受到受限势的限制作用会体现出特殊的物理特性,在实验中发现量子阱的生长方向受限势必须是强受限势而另外两个方向为非强受限势,所以本文在量子阱的生长方向施加非对称半指数受限势构成了非对称半指数势量子阱,为了深入了解非对称半指数量子阱的结构特征,在其垂直量子阱的生长方向施加各向异性抛物势,同时又增加了磁场对量子阱中电子的限制作用,研究了磁场对该量子阱中弱耦合极化子的影响。通过两次幺正变换和线性组合算符推导出弱耦合极化子的振动频率随抛物势的x与y方向的受限强度、磁场的回旋频率及非对称半指数受限势的两个参数的变化关系。并以处在非对称半指数量子阱中的GaAs半导体晶体进行模拟计算,结果表明:当x与y方向的受限强度及磁场的回旋频率取定值时非对称半指数量子阱中弱耦合极化子的振动频率是受限势参量U_0的增函数,而它是另一个参量σ的减函数,参数的改变是电子声子间耦合加强促进了极化子的形成。当磁场回旋频率及参量U_0和σ取定值时,极化子的振动频率是各向异性抛物势的x方向和y方向的受限强度的增函数,这体现了量子的尺寸限制效应,此外,由于磁场回旋频率随磁场的增大而增大,磁场回旋频率增大时会使极化子受到更强的约束作用,所以振动频率加强。当y方向的受限强度及参量U_0和σ取定值时极化子的振动频率是磁场的回旋频率的增函数。     

量子点接触中的电导与热功率：磁场与温度的影响

在有限温度和不同磁场下，精确计算了各种鞍形量子点接触中的量子化电导和热功率.量子点接触的形状影响体系的量子化特征.随磁场的增加，量子化电导的台阶加宽，热功率共振峰之间的距离加长，共振峰的数量减少.当温度升高时，电导的量子化被破坏，热功率的峰状结构也逐渐消失. 关键词： 量子点接触 量子化电导 热功率 磁场     

表面磁极化子的回旋共振性质

在磁场中有不少的极性晶体,电子和体纵光学声子的耦合弱,而与表面光学声子的耦合强。本文讨论电子和体纵光学声子耦合弱,与表面光学声子耦合强时对表面磁极化子的性质的影响。采用改进了的线性组合算符法导出了磁场中表面极化子的回旋共振频率和回旋共振质量,对AgCl晶体进行了数值计算。结果表明,磁场中表面极化子的回旋共振频率和回旋共振质量随磁场的增加而增加。     

用Ξ形四能级模型研究非对称耦合量子阱非定域激子复合发光

基于Ξ形四能级模型运用密度矩阵方程研究了非对称量子阱中非定域激子复合发光特性.理论结果表明：非定域激子复合发光具有双峰特征，两峰相对于中心跃迁频率的红移和蓝移量与电子和空穴的振荡频率密切相关.与单量子阱相比，这种频率移动对外加电场相当敏感，即当外加反向电场作小的变化时，两峰有较大的移动，表现强量子限域斯塔克效应.这意味着利用非对称量子阱在新一代高速调制器和光开关中具有潜在的应用价值. 关键词： 非对称耦合量子阱 共振隧穿 非定域激子 量子限域斯塔克效应     

限制环境下类氢体系的共振增强现象

采用B样条方法，以囚禁于巴基球内的Be³⁺为例，计算了限制环境下类氢体系 在不同外阱形状和位置下2s—3p振子强度随外阱深度的变化.2s，3p态都被限制在外阱时出 现共振增强，在坍塌点发现共振增强峰.计算结果表明，共振增强现象对外阱形状不敏感， 但是对外阱的限制能力有要求，同时还受到外阱位置的影响. 关键词： B样条 巴基球 振子强度 共振增强     

磁场下超晶格的子带结构及光跃迁

用有效质量方法计算了磁场下超晶格的子带结构和光跃迁。详细地介绍了计算方法,计算了磁能级的能量随磁场和阱宽的变化。发现随磁场和阱宽的增加,轻空穴态的混入就越显著,只有最低的三个重空穴态还基本保持原来的特性。计算中还发现第三轻空穴带对得到收敛的解是必不可少的。最后讨论了磁光跃迁几率和迴旋共振的有效质量。 关键词：     

δ-掺杂Be受主GaAs/AlAs多量子阱的空穴共振隧穿（英文）

三个具有不同量子阱宽度的GaAs/AlAs多量子阱结构样品通过分子束外延生长设备生长在半绝缘的(100)p-型GaAs衬底上,并且在量子阱层结构的生长过程中,在GaAs阱层中央进行了Be受主的δ-掺杂。基于这3个结构样品,通过光刻技术和半导体加工工艺制备了相应的两端器件。在4～200 K的温度范围内,我们分别测量了器件的电流-电压特征曲线,清楚地观察到了重、轻空穴通过δ-掺杂Be受主GaAs/AlAs多量子阱结构的共振隧穿现象。发现随着GaAs量子阱层宽的逐渐减小,轻空穴的共振隧穿峰向着高电压方向移动,这个结果和通过AlAs/GaAs/AlAs双势垒结构模型计算的结果是一致的。然而,随着测量温度的进一步升高,两个轻空穴共振峰都朝着低电压的方向移动,并且在150 K温度下,其中一个共振遂穿峰表现为一种振动模式。     

电场对量子阱中强耦合磁极化子性质的影响

研究了量子阱中强耦合磁极化子在电场作用下的性质,采用线性组合算符及幺正变换的方法导出了强耦合磁极化子的振动频率λ和基态能量E₀.讨论了强耦合磁极化子的基态能量与阱宽、电场强度、回旋频率之间的关系.通过数值计算,结果表明:强耦合磁极化子的基态能量的绝对值随着阱宽的增加而减小,随着外加电场强度的增加而增加;磁极化子的基态能量的绝对值随着磁场的回旋频率的增加而增加;磁场的回旋频率随着磁极化子的振动频率的增加而增加.     

HT-7 装置回旋质谱探测器边界离子诊断

介绍了回旋质谱探测器的原理和设计及其在HT-7 装置欧姆放电下对边缘等离子体中离子的诊断实验。探测器安装在限制器附近, 通过一小孔引进等离子体; 设置的前置偏压使电子和离子分离, 并使离子减速; 进入腔体内部的离子在射频电场和平行磁场的作用下发生回旋共振; 通过考察收集的离子电流信号中的共振峰可得到离子的荷质比、回旋频率等参数。实验中观察到荷质比为1、0. 5、0. 3333、0 . 1819 的离子共振峰。     

椭球型等能面电子回旋共振有效质量的计算

计算了椭球型等能面的回旋共振有效质量.证明了回旋共振有效质量与垂直于外磁场的截面选取无关.当外磁场的方向确定时,椭球型等能面上所有电子的回旋共振有效质量相等.     

Impurity related optical properties in tuned quantum dot/ring systems

In this paper, we explore the linear, third-order nonlinear, and total optical absorption coefficient (OAC) and refractive index change coefficient (RICC) of a GaAs doped quantum dot/quantum ring (QD/QR) with parabolic-inverse squared potential in conjunction with modified Gaussian confinement and taking into account the presence of on-centre shallow donor and or acceptor impurity. Calculations are done via the compact density matrix formalism and the iterative method. The two-dimensional parabolic QD/QR is subjected to uniform magnetic field oriented perpendicularly to the plane of the structure. The energy levels and wave function are derived within the framework of effective-mass and parabolic band approximation. The results exhibit that the OACs and RICC are clearly affected by different parameters of the applied confinement, strength of magnetic field, and the presence of impurity. The variation of confinement potential, nature of impurity, dot radius, cyclotron frequency of the parabolic confinement potential, and geometric parameter of the on-centre repulsive potential lead to either a red-shift or a blue-shift of the resonant peaks of the OACs and of the maximum and minimum of the RICC together with significant variations of the magnitudes of these resonant structures.     

Quantum waves in zinc

The effect of quantization of charge carriers in a magnetic field on the wave properties of zinc is investigated theoretically. It is shown that the cyclotron absorption by holes in the microwave range acquires a clearly manifested quantum structure: the absorption as a function of the magnetic field has the form of a sequence of narrow quantum peaks separated by deep minima. The suppression of cyclotron absorption at the minima is so strong that the propagation of an electron doppleron—the mode characterized by strong damping under classical conditions and not observed in zinc—becomes possible.     

抛物量子点中弱耦合磁极化子的性质

应用线性组合算符和幺正变换方法研究了抛物量子点中磁极化子的基态性质。得出基态能和基态束缚能随有效束缚强度增大而减小,随回旋频率增大而增大。当有效柬缚强度给定,基态能量随电子-体纵光学声子耦合强度增加而减小。当有效束缚强度l0>0.3时,电子-体纵光学声子耦合强度的变化对量子点中弱耦合磁极化子的基态能量的影响变得显著。当有效束缚强度l0<0.3时,电子-体纵光学声子耦合强度的变化对基态能量影响很小。由于有效束缚强度与量子点受限强度的平方根成反比,所以量子点受限越强,基态能量、基态束缚能越大,电子一体纵光学声子耦合强度和磁场的变化对量子点的影响相对越小;当量子点受限变弱时,电子-声子耦合强度变化对量子点的影响变大,磁场对量子点的影响也变大,所以在量子点中,极化子对量子点的影响不容忽略。     

抛物量子点中强耦合磁极化子的性质

采用Pekar类型的变分方法研究了抛物量子点中强耦合磁极化子的基态和激发态的性质。计算了基态和激发态磁极化子的束缚能以及磁极化子的共振频率。讨论了这些量对回旋频率和有效限制强度的依赖关系,以及磁极化子光学声子平均数的性质,结果表明:由于Zeeman劈裂,抛物量子点中磁极化子的回旋共振频率劈裂为两支。基态和激发态磁极化子的束缚能以及磁极化子的共振频率都随回旋频率的增加而增大,随量子点的有效束缚强度的增大而减小。     

Influence of an electric field on the magnetoabsorption in a field of resonant laser radiation

The frequency dependence of the coefficient of interband magnetoabsorption of a weak electromagnetic wave propagating in a constant electric field and in a field of resonant laser radiation at a frequency equal to the cyclotron frequency (infrared magnetic resonance) is calculated. The specific features observed in interband absorption of the electromagnetic wave in a uniform electric field are considered for the case in which the frequency of laser radiation is equal to the confinement frequency in a parabolic quantum well (infrared quantum-well resonance).     

Magneto-tunneling spectroscopy of GaAs---AlGaAs double barrier tunneling devices in pulsed high magnetic fields up to 40T

The magneto-tunneling effect was investigated in GaAs---AlGaAs double barrier resonant tunneling devices in pulsed high magnetic fiels up to 40T applied parallel(B) and perpendicular (B) to the barrier layers. In a sample with , oscillatory structures due to the 2D electrons in the emitter and the LO phonon assisted resonant tunneling were observed when the magnetic field (B) was swept at constant bias voltages. A large drop of the current was found in the quantum limit at applied voltages below the negative differential conductivity region. A striking hysteresis was observed in the voltage-current (V - I) curves. In a wide well sample with , rich structures were observed in the V - I curve for B, corresponding to the tunneling to different cyclotron orbits from the emitter.     

Magneto infrared absorption in high electron density GaAs quantum wells

Magneto infrared absorption measurements have been performed in a highly doped GaAs quantum well which has been lifted off and bonded to a silicon substrate, in order to study the resonant polaron interaction. It is found that the pinning of the cyclotron energy occurs at an energy close to that of the transverse optical phonon of GaAs. This unexpected result is explained by a model taking into account the full dielectric constant of the quantum well.     

磁场对非对称量子点中极化子性质的影响

采用线性组合算符和幺正变换方法研究磁场对非对称量子点中弱耦合磁极化子性质的影响.导出了非对称量子点中弱耦合磁极化子的振动频率、基态能量和基态结合能随量子点的横向和纵向有效受限长度、磁场和电子-声子耦合强度的变化关系.数值计算结果表明:非对称量子点中弱耦合磁极化子的基态能量和基态结合能随量子点的横向和纵向有效受限长度的增加而迅速增大.随回旋频率的增加而增大,随电子-声子耦合强度的增加而减小.     

Magnetic field dependence optical properties of GaN/AlN multiple quantum wells

In this work, we have investigated the optical properties of some multiple quantum wells under the influence of an external magnetic field and (for the first time) number of wells. We have retained the total length of the structure constant which is technologically important. Then we have detected a blue shift in the absorption peak positions due to the application of the magnetic field and a red shift due to the increasing of the number of wells. The red shift is only seen in the multiple quantum wells with odd number of wells and the absorption peaks of the multiple quantum well with even number of wells are not changed.     

电子横向运动对共振隧穿的影响

讨论了电子横纵方向运动耦合时的隧穿现象,对CdSe/Zn1-xCdxSe方形双势垒结构和抛物形双势垒结构的数值计算表明,在零偏压和非零偏压情况下,电子横向运动对共振隧穿的影响是不容忽略的。