Effects of electron- and impurity-ion-LO phonon couples on the impurity states in cylindrical quantum wires

The variational method and the effective mass approximation are used to calculate the phonon effects on the hydrogenic impurity states in a cylindrical quantum wire with finite deep potential by taking both the couplings of the electron-confined bulk longitudinal optical (LO) phonons and the impurity-ion-LO phonons into account.The binding energies and the phonon contributions are calculated as functions of the transverse dimension of the quantum wire. The results show that the polaronic effect induced by the electron-LO phonon coupling and the screening effect induced by the impurity-ion-LO phonon coupling tend to compensate each other and the total effects reduce the impurity binding energies.     

Scattering of electrons by confined interface polar optical phonons in a double-barrier heterostructure

It is shown that capture of the surface (interface) phonons can occur in a double-barrier heterostructure in addition to the capture of bulk polar optical phonons. The strength of interaction of electrons with confined interface phonons becomes lower as the thickness of the phonon well (a semiconductor layer where phonons are captured) is decreased. A new approach is suggested for reducing the scattering of electrons by polar optical phonons in a double-barrier quantum well; this approach is based on separate capture of phonons in narrow phonon wells. The calculated scattering rate with the capture of interface phonons into the GaAs/InAs/GaAs and AlAs/GaAs/AlAs quantum wells taken into account is found to be much lower than the rate obtained in the approximation of scattering of electrons by bulk phonons. A multifold decrease in the rate of electron-phonon scattering in the AlAs/GaAs/AlAs quantum well is obtained by separating this well by the monomolecular InAs layer that is transparent for electrons but acts as a reflecting barrier for polar optical phonons.     

An increase in the electron mobility in the two-barrier AlGaAs/GaAs/AlGaAs heterostructure as a result of introduction of thin InAs barriers for polar optical phonons into the GaAs quantum well

Confinement and localization of optical phonons in narrow phonon wells with thin phonon barriers decreases the rate of electron-phonon scattering by polar optical phonons by a factor of many times. An increase in mobility and drift velocity of electrons is experimentally observed in strong electric fields upon introduction of thin phonon barriers into the AlGaAs/GaAs/AlGaAs quantum well.     

Carrier energy relaxation time in quantum-well lasers

Carrier energy relaxation via carrier-polar optical phonon interactions with hot phonon effects in multisubband quantum-well structures is theoretically studied by using both bulk longitudinal optical phonons and confined longitudinal optical phonons. We find that the width and the depth of quantum wells only have moderate effects on carrier energy relaxation rates. Our results also indicate that the difference of energy relaxation rates between the quantum well and the bulk material is not significant. We investigate the effects of longitudinal optical phonon lifetimes on the carrier energy relaxation rate. Neglect of the finite decay time of longitudinal optical phonons will significantly underestimate the carrier energy relaxation time; this not only contradicts the experimental results but also severely underestimates the nonlinear gain coefficient due to carrier heating. The implications of our theoretical results in designing high-speed quantum-well lasers are discussed     

纳米晶体颗粒的声子布里渊光谱研究

以声子格林函数理论为基础,推导了简立方纳米晶体颗粒的声子布里渊光谱的线形公式,并给出了数值计算的结果。计算结果表明,在纳米晶体颗粒中,声子能带分裂为一系列能级,由于平移对称性被破坏,准动量不再守恒,除了长波长声子外,短波长声子也参与了布里渊散射,致使布里渊光谱发生了分裂和蓝移,分裂间隙和蓝移随纳米晶体颗粒尺寸的减小而增加,该项研究成果可应用于纳米晶体颗粒尺寸的测量。     

盘型量子点中极化子的温度效应

在考虑电子与体纵光学声子强耦合的条件下,通过求解能量本征方程,得出了盘型量子点中电子的基态能量、第一激发态能量及其相应的本征波函数;采用幺正变换和元激发理论方法研究了圆盘型量子点的声子效应,并讨论了温度对量子盘中极化子性质的影响。数值计算表明：在温度较低时,声子不能被激发,温度对能量无影响,当温度较高时,声子能够被激发,且温度愈高,被激发的声子数愈多,极化子能量愈大;结果还表明基态能量随着电子-声子耦合强度的增大而减小,随量子盘半径的增大而减小. 说明量子盘具有明显的量子尺寸效应。     

n层耦合量子阱中的极化光学声子振动:电-声子相互作用哈密顿

在介电连续近似下，推导和讨论了任意层的耦合量子阱系统中的受限纵光学(LO)声子模与界面光学(IO)声子模．为了描述受限纵光学声子的振动，采用了一个正确的LO声子势函数，同时，为了处理系统中的界面光学声子，采用了行列式解线性方程组的方法，得到了量子化的LO与IO声子场以及它们的电-声子相互作用哈密顿．本项工作可以看作是对以前一些工作的普遍化，它提供了一种解决声子效应对多层耦合量子阱系统影响问题的统一方法．     

探索量子微结构的新阶段

概述了超薄层量子结构中的量子效应及其器件之后，以立体量子微结构为重点，介绍了其中的电子的波动行为，例如普适的电导波动、弹性散射和声子散射的抑制等，并简要介绍了量子线和量子箱激光器以及电子波衍射晶体管，还讨论了对量子微结构的尺寸要求。     

Study of phonons in self-organized multiple Ge quantum dots

Raman scattering measurements were carried out in a self-organized multi-layered Ge quantum dot sample, which was grown using solid-source molecular-beam epitaxy, and consisted of 25 periods of 20-Å-high Ge quantum dots sandwiched by 20-nm Si spacers. The Ge-Ge optical phonon mode was found at 298.2 cm^?1, which was tuned by the phonon confinement and strain effects. Acoustic phonons related to Ge quantum dots have also been demonstrated.     

Topological Phononics: From Fundamental Models to Real Materials

Effective manipulation of phonons is crucial to modern energy‐information science and technologies but limited by the charge neutral and spinless nature of phonons. Recently, novel quantum concepts, including Berry phase, topology, and pseudospin, are introduced to phonon systems, providing fundamentally new routes to control phonons, opening an emerging field of “topological phononics.” Here, the basic concepts of Berry phase, topology, and pseudospin for phonons are introduced. Also, recent research progresses on various phononic topological states are reviewed, including phononic Su‐Schrieffer‐Heeger‐like states in 1D, quantum anomalous Hall‐like states, quantum valley Hall‐like states, and quantum spin Hall‐like states in 2D, and phononic Weyl points, nodal lines, and topological insulators in 3D. In addition to the fundamental models, material realizations and potential applications of topological phononics are comprehensively presented.     

抛物量子点中弱耦合极化子声子色散效应

利用线性组合算符和幺正变换相结合的方法,研究了声子色散对抛物量子点中弱耦合极化子性质的影响．计及体纵光学（LO）声子抛物色散,导出了量子点中极化子的基态能量和自陷能随量子点有效受限长度、电子-纵光学声子耦合常数和声子色散系数的变化关系．数值计算结果表明基态能量随声子色散系数的增大而减小,而自陷能随声子色散系数的增大而增大．     

极性半导体量子点中双极化子LO声子平均数的温度依赖性

采用Huybrechts线性组合算符法和Lee-Low-Pines变分方法研究了极性半导体量子点中双极化子性质的温度依赖性,推导出了量子点中双极化子的LO声子平均数的表达式。数值计算结果表明,双极化子的LO声子平均数随两电子间相对距离的增大或温度的升高而减小,随电子-LO声子耦合强度的增加而增大;两电子间的相对距离、电子-LO声子耦合强度和温度是影响双极化子束缚态稳定性的重要因素。     

The role of interface phonons in the formation of polaron states in quantum wells

A theory of a large-radius polaron in a quantum well is developed with consideration of the interaction of charged particles with different branches of the phonon spectrum. It is shown that, in narrow quantum wells, the major contribution to the polaron binding energy is made by interaction with symmetric interface phonons. As a result of such interaction, the polaron binding energy is defined by the effective mass of charge carriers in the quantum well and by the polarization properties of barriers. The possibilities of the formation of a polaron exciton in a quantum well in the case of strong interaction of charged particles with optical phonons are analyzed. The conditions in which the polarization fields produced by the electron and hole do not substantially compensate each other are established.     

压力下极化子效应对有限深量子阱中施主结合能的影响

考虑压力及屏蔽效应,同时计入量子阱结构中三类光学声子模(局域类体光学声子、半空间类体光学声子和界面光学声子)的作用,利用改进的LLP中间耦合方法处理电子-声子相互作用,讨论有限深量子阱中极化子效应对杂质态结合能的影响.结果表明,极化子效应使杂质态结合能明显降低,但压力使极化子效应减弱,屏蔽对极化子效应的影响不明显.     

简立方单原子纳米晶体颗粒声子结构研究

应用Dyson方程了简立方单原子纳米晶体 颗粒的声子格林函数。以些为基础,研究了简立方纳米晶体颗粒的声子结构,计算了其声子能级和声子态密度。计算结果表明,由于量 子尺寸效应,在纳米晶体颗粒,声 子能带分裂为一系列能级,随着纳米晶体颗粒尺寸的减小,声子能级分裂越为显著。     

简立方单原子纳米晶体颗粒的声子结构研究

应用Dyson方程推导了简立方单原子纳米晶体颗粒的声子格林函数。以此为基础,研究了简立方纳米晶体颗粒的声子结构,计算了其声子能级和声子态密度。计算结果表明,由于量子尺寸效应,在纳米晶体颗粒中,声子能带分裂为一系列能级,随着纳米晶体颗粒尺寸的减小,声子能级分裂越为显著。     

Interaction of phonons with iron-group ions

The interaction of phonons with paramagnetic spin systems is best characterized by coupling constants which relate the energy shift in the spin system to the strain introduced into the lattice. The theory of spin-phonon interactions is reviewed, and the coupling constants, as experimentally obtained, are compared to those which are most conveniently calculated. Generally, the results calculated on the basis of the point-charge theory are in reasonable agreement with the experimental results. A number of special topics involving spinophonon interactions are discussed, including double quantum detection of phonons, propagation in a dispersive medium, and the phonon maser.     

Effective mass of the ground state of the strong-coupling exciton in a quantum well

The properties of the effective mass of the ground state of the exciton, for which the electron (hole) is strongly coupled with interface-optical (IO) phonons but weakly coupled with bulk-longitudinal-optical (LO) phonons in a quantum well, are studied by means of Tokuda’s improved linear combination operator and a modified second Lee-Low-Pines transformation method. The results indicate that the contributions of the interaction between the electron (hole) and the different phonon branches to the effective ...     

GaN/AlN量子阱中的准受限声子

采用基于宏观介电连续模型的传递矩阵方法研究了任意层纤锌矿量子阱中的准受限声子，得出了任意层纤锌矿量子阱中的准受限声子的本征模解、色散关系；对GaN／A1N单量子阱和耦合量子阱中的准受限声子的色散关系进行了数值计算和讨论。实验发现在阱内的受限行为导致了波矢qe,j的量子化，并且准受限声子的色散随量子阶数m的减小而增强，由色散曲线组成的带随m的增加而变窄。     

有限温度及任意磁场强度下量子阱中的磁极化子(英文)

Taking into account the interaction of an electron with both bulk longitudinal-optical and surface longitudinal-optical phonons, we study the temperature dependence of the properties of a magnetopolaron in a quantum well in arbitrary magnetic field strength at a finite temperature. It is indicated that the temperature dependence of the self-trapping energies of the magnetopolaron is tremendously related to the strength of the magnetic field. The results also show that the electron-surface LO phonon interaction as well as the electron-bulk LO phonon interaction play important roles, especially when the quantum well width is getting thinner.