GaAs高过超能量态电子自旋相干动力学研究

Spin Coherence Dynamics of Electron with High Excess Energy in GaAs

研究了9.6K低温下、本征GaAs高过超能量态电子自旋相干动力学的浓度依赖,发现当光子能量为1.57eV,载流子浓度增大至2.65×1017cm-3时电子自旋相干量子拍的相位翻转180°。理论计算表明量子拍的相位翻转为区分轻、重空穴系统提供了重要依据,当载流子浓度大于2.6×1017cm-3时,量子拍的振幅主要起源于重空穴价带-导带跃迁,当载流子浓度小于2.6×1017cm-1时,量子拍的振幅主要起源于轻空穴价带-导带跃迁。因而,分别在轻空穴价带-导带系统和重空穴价带-导带系统实验测量电子自旋相干动力学成为可能,实验数据表明在轻空穴价带-导带系统测得的电子自旋相干弛豫时间明显大于在重空穴价带-导带系统测得的电子自旋相干弛豫时间。

Time resolved circularly polarized pump probe spectroscopy is used to study the carrier density dependence of the electron spin coherence dynamics in intrinsic GaAs at 9.6 K.It is found that the phase of the quantum beats is altered by 180° when the carrier density is increased to 2.65 × 1017 cm-3 with the photon energy of 1.57 eV.Theoretical calculation shows that the phase reversal of quantum beats provides the key information to distinguish the heavy hole and light hole systems,when the carrier density is larger than 2.6 × 1017 cm-3,the quantum beats mainly originates from the heavy hole valance band conduction band transitions,otherwise,the quantum beats mainly originates from the light hole valance band conduction band transitions,thus spin coherence dynamics in heavy hole valance band and light hole valance band conduction band systems can be measured separately,the experimental data shows that spin coherence relaxation time measured in heavy hole valance band conduction band system is larger than thatmeasured in light hole valance band conduction band system.