Hanle effect in (In,Ga)As quantum dots: Role of nuclear spin fluctuations
Hanle effect in (In,Ga)As quantum dots: Role of nuclear spin fluctuations
复制标题
(In,Ga)As 量子点中的汉勒效应：核自旋涨落的作用
DOI：
10.1103/physrevb.87.235320
复制
发表时间：
2013
影响因子：
3.7
通讯作者：
M. Bayer
中科院分区：
文献类型：
--
作者：
M. S. Kuznetsova;K. Flisinski;I. Gerlovin;I. Ignatiev;K. Kavokin;S. Verbin;D. Yakovlev;D. Reuter;A. Wieck;M. Bayer
研究了(In，Ga)As量子点中核自旋涨落在电子对核自旋动态极化中的作用。研究了横向磁场中圆偏振光泵浦(Hanle效应)下的光致发光偏振。利用平行于光轴的弱附加磁场来控制核自旋冷却效率和核自旋温度符号。汉勒曲线的形状随着这个控制场的改变而急剧改变，正如早先在块状半导体和量子阱中观察到的那样。然而，标准的核自旋冷却理论在平均核磁场(Overhauser场)下工作，不能描述在一定控制场范围内的实验Hanle曲线。这一争议是通过考虑量子点中有限数量的核所引起的核自旋波动来解决的。我们提出了一个模型，描述了在核自旋涨落的随机Overhauser场中，电子自旋经历快速矢量进动后对核自旋系统的冷却。该模型使我们能够准确地描述测量的Hanle曲线，并确定所研究量子点的电子-核自旋系统的参数。
The role of nuclear spin fluctuations in the dynamic polarization of nuclear spins by electrons is investigated in (In,Ga)As quantum dots. The photoluminescence polarization under circularly polarized optical pumping in transverse magnetic fields (Hanle effect) is studied. A weak additional magnetic field parallel to the optical axis is used to control the efficiency of nuclear spin cooling and the sign of nuclear spin temperature. The shape of the Hanle curve is drastically modified with changing this control field, as observed earlier in bulk semiconductors and quantum wells. However, the standard nuclear spin cooling theory, operating with the mean nuclear magnetic field (Overhauser field), fails to describe the experimental Hanle curves in a certain range of control fields. This controversy is resolved by taking into account the nuclear spin fluctuations owed to the finite number of nuclei in the quantum dot. We propose a model describing cooling of the nuclear spin system by electron spins experiencing fast vector precession in the random Overhauser fields of nuclear spin fluctuations. The model allows us to accurately describe the measured Hanle curves and to determine the parameters of the electron-nuclear spin system of the studied quantum dots.