GaAs中电子自旋极化的浓度依赖研究

采用时间分辨圆偏振光抽运-探测光谱,研究本征GaAs中导带底附近电子初始自旋极化和自旋弛豫动力学.发现电子初始自旋极化度小于通常认为的0.5,并随光注入载流子浓度的增大而减小.假设右旋圆偏振光激发到导带的自旋取向,向上与向下电子浓度之比为13,理论计算的电子初始自旋极化度随载流子浓度变化关系与实验结果很好的符合.计算结果同时表明,带隙重整化效应对电子初始自旋极化度有较大影响,但电子初始自旋极化度小于0.5的现象并非起源于带隙重整化效应.

Density dependence of the electron spin polarization in GaAs

Time-resolved circularly polarized pump-probe spectroscopy is used to study the carrier density dependence of the electron spin polarization dynamics in intrinsic GaAs near the bottom of the conduction band. It is found that the initial degree of the electron spin polarization is less than 0.5, and decrease with the carrier density. On the assumption that the number of spin-down electrons is three times as many as the number of spin-up electrons if the pump beam have right hand circular polarization, the carrier-density dependence of the initial degree of spin polarization calculated theoretically agree well with the experimental results. The theoretical calculation shows that the band-dap renormalization effect has a significant influence on the initial degree of spin polarization, but it is not the physical origin that results in the initial degree of the electron spin polarization less than 0.5.