本征砷化镓量子阱的瞬态自旋光栅中电子自旋扩散研究

Study of electron spin diffusion in transient spin diffraction gratings in intrinsic GaAs quantum wells

利用瞬态自旋光栅方法,在室温下实验研究了本征GaAs量子阱中电子自旋扩散的动力学过程.测得了不同周期的瞬态自旋光栅的衰减率,根据普遍认同的公式:Γ=q2Ds+l/τs,计算得到电子自旋扩散系数Ds=104 cm2/s,以及电子自旋弛豫时间τs=46 ps.测得的电子自旋扩散系数与文献报道的N型GaAs量子阱的实验测量结果相吻合,说明样品导电类型对电子自旋扩散系数没有显著影响.而电子自旋弛豫时间τs=46 ps与由饱和吸收方法测得的结果:τs=103 ps有明显区别.进一步分析了自旋光栅调制度随时间的衰减规律,对自旋极化衰减率公式:Γ=q2Ds+l/τs进行了修正.

A time-resolved transient spin diffraction gratings spectroscopy was developed, and used to study transient spin diffraction gratings dynamics in intrinsic GaAs quantum wells. The spin coefficient of D, = 104 cm2/s and spin relaxation time of ~＇, =46 ps were obtained by the results of our experiment and the well-known formula： F = q2D, ＋ l/T, . We found the former （D, = 104 cmZ/s） in reasonable agree with in n type GaAs quantum wells, while the later （T2 = 46 ps） was much small than that measured by time-resolved saturation absorption spectroscopy（ T2 = 103 ps）. We further investigated on transient spin diffraction gratings dynamics and corrected the formula： F = q2D, ＋ l/T,