本征GaAs中电子自旋极化的能量演化研究

Energy-dependent evolution of electron spin polarization in bulk intrinsic GaAs

采用时间分辨圆偏振光抽运-探测光谱,研究9.6 K温度下本征GaAs中电子自旋相干弛豫动力学,发现反映电子自旋相干的吸收量子拍的振幅随光子能量的增加呈非单调性变化.考虑自旋极化依赖的带填充效应和带隙重整化效应,发展了圆偏振光抽运-探测光谱的理论模型.该模型表明量子拍的振幅依赖于所探测能级的电子初始自旋极化度,自旋探测灵敏度以及带填充因子,三者的乘积导致了量子拍振幅的非单调变化,与实验结果一致.给出了能级分裂的二能级系统中电子自旋极化度定义.发现在高能级上可以获得100%的初始电子自旋极化度.

Time-resolved circularly polarized pump-probe spectroscopy is used to study the electron spin coherence dynamics in intrinsic GaAs at 9.6 K. It is found that the oscillation amplitude of absorption quantum beats reflecting electron spin coherence varies nonmonotonically with photon energy increaing. A circularly dichromatic pump-probe model is developed with both spinpolarized-dependent band filling and band-gap renormalization effects taken into account. The model shows that the oscillation amplitude of quantum beats is dependent on the initial degree of electron spin polarization, spin-detectable sensitivity and bandfilling factor whose product results in the non-monotonic variation of the quantum-beat amplitude and agrees very well with our experimental results. The degree of electron-spin polarization involved in energy-split two-level system is defined for the first time. It is found that a degree of electron spin polarization of up to 100% can be photocreated at higher excess-energy levels.