抛物量子点中弱耦合磁极化子的性质

Property of Weak-coupling Magnetopolaron in a Parabolic Quantum Dot

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。

With recent rapid advances in nanofabrication technology it has become possible to confine electrons in all three spatial dimensions in semiconductors called quantum dots. The electron energy spectrum of such quantum dot is fully quantized. Such systems are of great interest in fundamental studies, as well as in practical applications for microelectronic devices. Electron-phonon interaction, which plays an important role in electronic and optical properties of polar crystalline materials in three dimensions, will have pronounced effects in low-dimensional systems as well. Recently there have been a considerable number of theoretical studies on the same effects including the confinement problem in quantum dot system. Zhu and Gu have studied the effect of an external magnetic field on zero-dimensional polarons in the weak-coupling limit using the second-order Rayleigh-Schrodinger perturbation theory, and found that for a strong magnetic fields, the cyclotron mass in a parabolic quantum dot is split into two cyclotron masses. Zhou has calculated both the ground state and the exited state energy of strong-coupling magnetoplorons in a disk-shape quantum dot with Peker-tape variational method. In this paper, we investigate weak-coupling magnetopolaron' s properties in a parabolic quantum dot by the linear combination operators in the first time. It is shown that the bound state energy and binding energy decrease with increasing the effective confined length of the quantum dot, and enhance with enlarging the cyclotron resonance frequency. The Fig. 1 and 2 present that the magnetopolaron ground state energy E0 of parabolic quantum dot is as a function of the effective confinement length and the cyclotron resonance frequency. The Fig. 3 and 4 indicate that the magnetopolaron binding energy |Eb| of parabolic quantum dot effect as a function of effective confinement length and the cyclotron resonance frequency. We can see that the confine effect of parabolic quantum dot strengthens the ground state energy and the binding energy.