共查询到20条相似文献,搜索用时 15 毫秒
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在有效质量近似下,考虑到外电场的影响,详细研究了直接带隙Ge/GeSi量子阱中带间光跃迁吸收系数和阈值能量随量子阱阱宽,外电场强度的变化情况。结果表明:随着外电场的增强,带间光跃迁吸收强度会逐渐减弱,阈值能量减小,吸收曲线向低能方向移动,出现了红移现象。此外,当量子阱比较大时,外电场对量子阱中带间光跃迁阈值能量的影响更加明显。 相似文献
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Impurity optical absorption in parabolic quantum well 总被引:1,自引:0,他引:1
Eduard M. Kazaryan Artavazd A. Kostanyan Hayk A. Sarkisyan 《Physica E: Low-dimensional Systems and Nanostructures》2005,28(4):423-430
Optical absorption in GaAs parabolic quantum well in the presence of hydrogenic impurity is considered. The absorption coefficient associated with the transitions between the upper valence subband and donor ground state is calculated. The impurity ground state wave function and energy are obtained using the variational method. Dependence of the absorption spectra on impurity position in quantum well was investigated. It is shown, that along with quantum well width decrease the absorption threshold shifts to higher frequencies. Results obtained within frames of parabolic approximation are compared with results for rectangular infinite-barrier quantum well case. The acceptor state → conduction band transitions considered as well. 相似文献
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《Physics letters. A》2014,378(32-33):2367-2370
Within the framework of partial-wave method, we study in this Letter the arbitrary l continuum states of the Schrödinger equation with the hyperbolic molecular potential in terms of an improved approximation to the centrifugal term. We present the normalized radial wave functions and obtain analytical formula of phase shifts. In addition, the corresponding bound states are also discussed by studying the analytical properties of the scattering amplitude. We calculate the energy spectra and scattering phase shifts by the improved, previous approximations and the accurate methods, respectively and find that the improved approximation is better than the previous one since the present results are in better agreement with the accurate ones. 相似文献
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Guanghui Liu Kangxian Guo Hassan Hassanabadi Liangliang Lu 《Physica B: Condensed Matter》2012,407(17):3676-3682
Linear and nonlinear optical properties in a disk-shaped quantum dot (DSQD) with a parabolic potential plus a hyperbolic potential in a static magnetic field are theoretically investigated within the framework of the compact-density-matrix approach and iterative method. The energy levels and the wave functions of an electron are obtained by three kinds of approximation methods. It is found that optical absorption coefficients and refractive index changes are not only by the characteristic parameters of the hyperbolic potential and the confinement frequency, but also by the magnetic field. 相似文献
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A new confinement potential for spherical quantum dots, called the modified Gaussian potential (MGP), is studied. In the present work, the following problems are investigated within the effective-mass approximation: (i) the one-electron energy spectra, (ii) wave functions, (iii) the problem of existence of a bound electron state, and (iv) the binding energy of center and off-center hydrogenic donor impurities. For zero angular momentum (l=0), the new confinement potential is sufficiently flexible to obtain analytically the spectral energy and wave functions. The results obtained from the present work show that (i) the new potential is suitable for predicting the spectral energy and wave functions, and (ii) the geometrical sizes of the quantum dot play the important roles on the energy levels, wave functions, the binding energy, and the existence of a bound electron state. 相似文献
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F. Ungan 《Journal of luminescence》2011,131(11):2237-2243
In the present work, the changes in the intersubband optical absorption coefficients and the refractive index in a modulation-doped quantum well have been investigated theoretically. Within the envelope function approach and the effective mass approximation, the electronic structure of the quantum well is calculated from the self-consistent numerical solution of the coupled Schrödinger-Poisson equations. The analytical expressions of optical properties are obtained by using the compact density-matrix approach. The numerical results GaAs/AlxGa1−xAs are presented for typical modulation-doped quantum well system. The linear, third-order nonlinear and total absorption and refractive index changes depending on the doping concentration are investigated as a function of the incident optical intensity and structure parameters, such as quantum well width and stoichiometric ratio. The results show that the doping concentration, the structure parameters and the incident optical intensity have a great effect on the optical characteristics of these structures. 相似文献
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We investigate the nonlinear modes in a rotating double well potential with 79T symmetry. Focus on the existence and stability of the nonlinear PT modes in this system, we found that five types of PT modes can stably exist by given certain parameter settings. The multistable area between these modes are studied numerically and the bistable and tristable areas are delimited. With different input trial wavefunctions, five types of solitary wave modes are identified. We found that the rotating of the potential can significantly affect the power flow of the fundamental harmonic mode, whose effect is absent for the other modes. 相似文献
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A. K. Atayan E. M. Kazaryan A. V. Meliksetyan H. A. Sarkisyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2010,45(3):126-131
We investigate magnetoexcitonic states in the Ga1−x
1Alx
1As/GaAs/Ga1−x
2Alx
2 As quantum ring with the Winternitz-Smorodinsky confinement potential. A homogeneous magnetic field is directed perpendicularly
to the ring plane. The Coulomb interaction between the electron and hole is assumed as weak and is considered in the framework
of perturbation theory. Obtained results show that the more realistic Winternitz-Smorodinsky confinement potential, which
takes into account a peculiar smoothing of the confinement potential profile, leads to raising of the electron energy levels
as compared to the case of a finite-height rectangular confinement potential. 相似文献
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Wenfang Xie 《Physics letters. A》2008,372(33):5498-5500
A investigation of the nonlinear optical properties of a hydrogenic donor in a disc-like parabolic quantum dot has been performed by using the matrix diagonalization method. The optical absorption coefficient between the ground (L=0) and the first excited state (L=1) have been examined based on the computed energies and wave functions. The results are presented as a function of the incident photon energy for the different values of the incident optical intensity and the confinement strength. We found the total optical absorption coefficient is strongly affected by the incident optical intensity and the confinement strength. 相似文献
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The linear and nonlinear optical properties in a three-dimensional anisotropic quantum dot subjected to a uniform magnetic field directed with respect to the -axis have been investigated within the compact-density matrix formalism and the iterative method. The dependence of the linear and nonlinear optical properties on the characteristic frequency of the parabolic potential, on the magnetic field, and on the incident optical intensity is studied in detail. Moreover, taking into account the position-dependent effective mass, the dependence of the linear and nonlinear optical properties on the dot radius is investigated. The results show that the optical absorption coefficients (ACs) and refractive index (RI) changes of the anisotropic quantum dot (QD) are strongly affected by these factors, and the position effect also plays an important role in the optical ACs and RI changes of the anisotropic QD. 相似文献
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Zhiping Wang Benli YuXuqiang Wu Shenglai ZhenZhigang Cao Jun Zhu 《Superlattices and Microstructures》2011,50(6):734-742
We investigate the transient behaviors of the dispersion and the absorption in a three-level GaAs/AlGaAs semiconductor quantum well system. It is found that the Fano interference and the energy splitting affect the transient behaviors dramatically, which can be used to manipulate efficiently the gain-absorption coefficient and group velocity of the probe field. The dependence of transient electron population on the Fano interference and the energy splitting is also discussed. 相似文献
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采用平面波展开、幺正变换和变分相结合的方法推导出有限深势阱里量子盘中极化子的基态能量公式.采用极化子单位进行数值计算,结果表明极化子的基态能量随势垒高度和势垒宽度的增大而增大,原因是势垒愈高、愈宽,电子穿透势垒的可能性愈小,导致电子能量增大,进而导致极化子基态能量增大.数值计算结果还表明极化子的基态能量随量子盘有效受限长度和量子盘半径的增大而减小;声子效应导致极化子能量较电子能量低. 相似文献
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The subband structure and optical properties of a cylindrical quantum well wire under intense non-resonant laser field are investigated by taking into account the correct dressing effect for the confinement potential. The energy levels and wave functions are calculated within the effective mass- approximation using a finite element method. It is found that the absorption coefficient and the saturation intensity are strongly affected by the laser amplitude and frequency as well as by the incident light polarization. As a key result, a large anisotropy in the linear and nonlinear optical absorptions for very intense laser field is predicted. These effects can be useful for the design of polarization sensitive devices. 相似文献
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In this paper we study inflationary dynamics with a scalar field in an inverse coshyperbolic potential in the braneworld model.
We note that a sufficient inflation may be obtained with the potential considering slow-roll approximation in the high energy
limit. We determine the minimum values of the initial inflaton field required to obtain sufficient inflation and also determine
the relevant inflationary parameters. The numerical values of spectral index of the scalar perturbation spectrum are determined
by varying the number of e-foldings for different initial values of the inflaton field. The result obtained here is in good
agreement with the current observational limits.
相似文献
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Nonlinear optical properties of semiconductor quantum wires 总被引:1,自引:0,他引:1
V. Dneprovskii E. Zhukov V. Karavanskii V. Poborchii I. Salamatina 《Superlattices and Microstructures》1998,23(6):1217-1221
Nonlinear optical transmission at discrete frequencies (bleaching bands) has been observed in CdSe and GaAs quantum wires crystallized in chrysotile asbestos nanotubes with average diameter ≈ 6 nm and in nanocrystals of CdS (crystallized in the transparent molecular filter—mica with empty channels of designed diameter). The induced decrease of absorption in quantum wires has been explained by filling of the size-quantized energy bands with nonequilibrium carriers (saturation effect) and by the phase-space filling of excitons. 相似文献
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The persistent diamagnetic current in a GaAs quantum dot with Gaussian confinement is calculated. It is shown that except at very low temperature or at high temperature, the persistent current increases with decreasing temperature. It is also shown that as a function of the dot size, the diamagnetic current exhibits a maximum at a certain confinement length. It is furthermore shown that for a shallow potential, the persistent current shows an interesting maximum structure as a function of the depth of the potential. At low temperature, the peak structure is pretty sharp but becomes broader and broader with increasing temperature. 相似文献
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We have performed Hartree-Fock calculations of the electronic structure of N ≤ 10 electrons in a quantum dot modeled with a confining Gaussian potential well. We discuss the conditions for the stability
of N bound electrons in the system. We show that the most relevant parameter determining the number of bound electrons is V
0
R
2. Such a feature arises from widely valid scaling properties of the confining potential. Gaussian Quantum dots having N = 2, 5, and 8 electrons are particularly stable in agreement with the Hund rule. The shell structure becomes less and less
noticeable as the well radius increases.
相似文献