EXCITON-BOUND ELECTRON-SPIN RELAXATION
EXCITON-BOUND ELECTRON-SPIN RELAXATION
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激子束缚电子自旋弛豫
DOI：
10.1103/physrevb.56.9259
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发表时间：
1997
影响因子：
3.7
通讯作者：
G. Rocca
中科院分区：
文献类型：
--
作者：
E. A. D. A. E. Silva;G. Rocca
半导体量子阱中的激子发光偏振研究揭示了激子自旋弛豫的两种主要机制的共存：一种众所周知的直接弛豫，由于电子空穴交换相互作用而同时发生电子和空穴自旋翻转，以及一种间接弛豫，由于单粒子的顺序自旋翻转。该间接通道中的激子自旋弛豫速率受到较慢的单粒子自旋翻转速率（通常是电子自旋翻转速率）的限制。在这项工作中，提出了由导带中的自旋轨道分裂驱动的激子束缚电子自旋动力学理论。结果表明，仅在电子自旋方向上不同的光学活性和非活性激子态之间的非对角矩阵元素代表了当激子弹性散射并弛豫其自旋时随机变化的有效磁场。光学活性和非活性状态之间的交换分裂充当恒定的外部磁场，从而减少弛豫。束缚电子自旋翻转的估计速率与从先前的实验数据拟合获得的值非常吻合。还简要讨论了具有实空间间接激子的半导体异质结构，其中顺序自旋翻转弛豫通道成为主要结构，以及弛豫时间对阱宽度的依赖性。
Exciton luminescence polarization studies in semiconductor quantum wells have revealed the coexistence of two main mechanisms of exciton-spin relaxation: a well-known direct relaxation with simultaneous electron and hole spin flip due to the electron-hole exchange interaction and an indirect one with sequential spin flips of the single particles. The rate of exciton-spin relaxation in this indirect channel is limited by the slower single-particle spin-flip rate, which is typically the electron one. In this work a theory of exciton-bound electron-spin dynamics driven by the spin-orbit splitting in the conduction band is presented. It is shown that the off-diagonal matrix element between optical active and inactive exciton states that differ only with regard to the electron spin direction represents an effective magnetic field that changes randomly as the exciton is elastically scattered and relaxes its spin. The exchange splitting between the optical active and inactive states acts as a constant external magnetic field, reducing the relaxation. The estimated rate of the bound electron spin flip agrees well with values obtained from previous fittings of the experimental data. Semiconductor heterostructures with real-space indirect excitons, for which the sequential spin-flip relaxation channel becomes the dominant one, are also briefly discussed together with the dependence of the relaxation time on the well width.