施加电场的半抛物量子阱中的电光效应

利用量子力学中的紧致密度矩阵方法，研究了施加电场的半抛物量子阱中的电光效应。通过位移谐振子变换，得到了系统中的电子态的精确解。对典型的GaAs材料进行数值计算的结果表明，随着电场强度的增加，电光效应系数几乎线性随之增加；但是随着半抛物量子阱受限势频率的增加，电光效应系数单调地减小；而且在同样的电场强度及抛物束缚势频率作用下，半抛物量子阱模型中的电光效应系数比抛物量子阱模型中的值大两个数量级，这是由于我们所选模型本身的非对称性以及电场进一步使这种非对称性增强的缘故。     

施加电场的半抛物量子阱中的二阶非线性光学极化率

利用量子力学中的紧致密度矩阵方法,研究了施加电场的半抛物量子阱中的二阶非线性光学极化率(光整流系数),得到了此系统的光整流系数的解析表达式.数值计算的结果表明,随着电场强度的增加,光整流系数几乎线性随之增加,而且在同样的电场强度及抛物束缚势频率作用下,半抛物量子阱模型中的光整流系数比抛物量子阱模型中的值大一个数量级,这是由于我们所选模型本身的非对称性以及电场进一步使这种非对称性增强的缘故.     

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.     

加偏置电场的抛物量子阱中的电光效应

本文利用密度矩阵方法得到了加偏置电场的抛物量子阱中电光效应的解析表达式,并以典型的GaAs抛物量子阱为例进行了数值计算研究结果表明,电光效应随偏置电场和抛物势频率的增大而增强,同时也表明GaAs量子阱中的电光效应比体GaAs中的要强一个数量级以上。     

氮化物抛物量子阱中类氢杂质态能量

采用变分方法研究氮化物抛物量子阱(GaN/Al_xGa_1-xN)材料中类氢杂质态的能级,给出基态能量、第一激发态能量、结合能和跃迁能量等物理量随抛物量子阱宽度变化的函数关系.研究结果表明,基态能量、第一激发态能量、基态结合能和1s→2p±跃迁能量随着阱宽L的增大而减小,最后接近于GaN中3D值.GaN/Al_0.3Ga_0.7N抛物量子阱对杂质态的束缚程度比GaAs/Al_0.3Ga_0.7As抛物量子阱强,因此,在GaN/Al_0.3-Ga_0.7N抛物量子阱中束缚于杂质中心处的电子比在GaAs/Al_0.3Ga_0.7As抛物量子阱中束缚于杂质中心处的电子稳定.     

ZnSe/ZnS抛物量子阱中激子的极化子效应(英文)

采用推广的LLP方法研究了ZnSe/ZnS抛物量子阱中激子的极化子效应。考虑电子和空穴与LO声子的相互作用,得到了激子基态能量和结合能随阱宽的变化关系。结果表明,阱宽较小时,能量随着阱宽的增大而急剧减小;阱宽较大时,能量减小的比较缓慢。和我们以前的工作对比,我们发现ZnSe/ZnS抛物量子阱对激子的束缚强于GaAs/Ga1-xAlxAs抛物量子阱。     

外电场下应变量子阱中电子与空穴的本征态

考虑自发与压电极化引起的内建电场,自由电子-空穴气屏蔽效应和外加电场,基于常微分数值计算,自洽求解电子与空穴的薛定谔方程和泊松方程以获得基态能级。以典型的GaN/A lxGa1-xN纤锌矿氮化物应变量子阱为例,通过数值求解,得到电子与空穴的本征基态能和相应本征波函数。计算结果表明:沿量子阱生长方向所施加的外加电场将抵消阱中内建电场的作用,阱结构的弯曲程度略显平缓,使电子(空穴)本征波函数逆(顺)着外电场方向移动,且均向阱中心移动,波峰峰值增加,隧穿几率减小;在固定外电场情况下,电子与空穴基态能级随阱宽的增加而减小,随掺杂组分的增加而增加,表明外加电场对内建电场有所削弱以及量子限制作用对电子(空穴)基态能有显著的影响。     

一维多量子阱的能级

给出了一维多量子阱能级满足的超越方程,利用此方程可以求出任意一维势的束缚态能级．     

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.     

量子点量子阱中的三阶非线性光学特性的研究

利用紧致密度矩阵近似方法，研究了一个特殊量子点量子阱中的三阶非线性光学特性(三次谐波产生)，得到了量子点量子阱系统的三次谐波产生系数的解析表达式，而且考虑了量子点量子阱系统中的两种电子束缚态-壳层阱内与阱外两种束缚态。对CdS/HgS构成的典型的量子点量子阱进行了数值计算，得到了10^-15(m／v)^2量级的三次谐波产生系数，并且绘出了三次谐波产生系数作为量子点量子阱的尺寸和泵浦光子能量的函数曲线，最后对曲线的特征及其形成的原因进行了解析。     

Electronic energy levels in semiconductor quantum wells and superlattices

We present the results of the calculations of some electronic properties of semiconductor quantum wells and superlattices. The review includes the superlattice band structure and the quantum well bound energy levels; the virtual bound states of semiconductor quantum wells and their influence on the energy spectrum of separate confinement heterostructures. Finally the perturbation of quantum well bound states and exciton states by a static electric field applied parallel to the growth axis is considered.     

Static and dynamic study of magnetic properties in FeNi film on flexible substrate, effect of applied stresses

The influence of an external electric field on the binding energies of the ground state and excited states with the third-harmonic-generation (THG) coefficient for spherical quantum dot (QD) with parabolic confinement is investigated theoretically. The energy levels and wave functions of electronic states in the QDs are calculated using by variational method within the effective-mass approximation. The numerical results demonstrate that the THG coefficient very sensitively depends on the magnitude of the electric field and the radius of the QDs. In addition, the THG coefficient also depends on the relaxation rate of the spherical QD with parabolic confinement and the position of impurity.     

Electron-phonon effects on Stark shifts of excitons in parabolic quantum wells: Fractional-dimension variational approach

Electron-phonon effects on Stark shifts of excitons in parabolic quantum wells are studied theoretically by using a fractional dimension method in combination with a Lee-Low-Pines-like transformation and a perturbation theory. The numerical results for the exciton binding energies and electron-phonon contributions to the binding energies as functions of the well width and the electric field in the Al_0.3Ga_0.7As parabolic quantum well structure are obtained. It is shown that both exciton binding energy and electron-phonon contributions have a maximum with increasing the well width. The binding energy and electron-phonon contribution decrease significantly with increasing the electric-field strength, in special in the wide-well case.     

Exciton binding energy and excitonic absorption spectra in a parabolic quantum wire under transverse electric field

The effects of transverse electric field on the energy levels of electron and heavy hole, exciton binding energy and excitonic absorption spectra of GaAs parabolic quantum wire are theoretically investigated in detail. The results indicate that the electron and hole energy levels, exciton binding energy, excitonic absorption coefficient and absorption energy becomes smaller with the increase of electric field. That is more significant at the condition of weaker parabolic confinement potential. The phenomena can be explained by the separation of overlap integral of the electron and hole at the ground states.     

Electronic molecule-like spectrum of quantum wells in crossed fields

We show that an electron confined to a single finite parabolic quantum well in crossed electric and magnetic fields can behave as a double quantum well system. The magnetic field is parallel to the heterostructure layers and the electric field is perpendicular to those. For a suitable choice of both fields and quantum well width, the electron can be confined to a double quantum well effective potential that is very similar to the electronic potential model for diatomic molecules. The double quantum well spectrum is calculated using a numerical algorithm based on semiclassical methods. A physical interpretation of this quantum system is given based on the analogy to the electrons bound to diatomic molecules.     

抛物量子点中强耦合束缚磁极化子的性质

采用Pekar类型的变分方法研究了抛物量子点中强耦合束缚磁极化子的基态和激发态的性质.计算了束缚磁极化子的基态和激发态的能量、光学声子平均数以及束缚磁极化子的共振频率.讨论了这些量对回旋频率和有效束缚强度以及库仑束缚势的依赖关系.数值计算结果表明:量子点中强耦合束缚磁极化子的基态能量和共振频率以及光学声子平均数均随量子点的有效束缚强度的增加而减小,基态能量随库仑束缚势的增加而减小,随回旋频率的增加而增大.     

Long-lived resonances supported by a contact interaction in crossed magnetic and electric fields

The lifetime of the resonance states of an electron interacting with a zero-range potential in the presence of crossed magnetic and electric fields is studied for the case where the electron is confined in the direction of the magnetic field by a parabolic quantum well. It is shown that long-lived electric field-induced resonances exist in this system even when the zero-range potential does not support any field-free bound state. The relationship of these resonances with the Landau states localized near the point interaction is discussed.     

磁场对量子阱中弱耦合束缚极化子性质的影响

采用线性组合算符及幺正变换方法研究了磁场对量子阱中弱耦合束缚极化子的性质的影响。导出了量子阱中束缚极化子的基态能量与振动频率、库仑束缚势、磁场和阱宽之间的变化关系。同时也讨论了振动频率与库仑束缚势、磁场之间的变化关系。通过数值计算结果表明:量子阱中束缚极化子的基态能量因振动频率、库仑束缚势、磁场和阱宽的不同而不同,它随振动频率和磁场的增加而增大,随库仑束缚势和阱宽的增大而减小。量子阱中束缚磁极化子的基态能量与振动频率无关,随库仑束缚势和阱宽的增大而减小,随磁场的增大而增大。