Phonon-induced quantum ratchet in the exciton spin dynamics in diluted magnetic semiconductors in a magnetic field
Phonon-induced quantum ratchet in the exciton spin dynamics in diluted magnetic semiconductors in a magnetic field
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DOI：
10.1103/physrevb.99.075301
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发表时间：
2018-12
影响因子：
3.7
通讯作者：
F. Ungar;M. Cygorek;V. M. Axt
中科院分区：
文献类型：
--
作者：
F. Ungar;M. Cygorek;V. M. Axt
磁掺杂半导体以其巨大的塞曼分裂而闻名，即使在相对较小的外部磁场中也可以达到几个meV。通过光激发制备非平衡激子分布后，稀磁半导体量子阱中的自旋动力学通常由激子-杂质交换相互作用引起的自旋翻转散射过程控制。我们的理论计算表明，这些材料中的巨大塞曼分裂与纵向声学声子的影响相结合，导致量子棘轮型动力学，导致载流子自旋极化在极低温度下几乎完全逆转。此外，我们发现，一个更简单的速率方程方法的预测在质量上与一个更先进的、数值要求更高的量子动力学描述在广泛的温度范围内的自旋动力学一致，尽管数量上的差异是明显的。
Magnetically doped semiconductors are well known for their giant Zeeman splittings which can reach several meV even in relatively small external magnetic fields. After preparing a nonequilibrium exciton distribution via optical excitation, the spin dynamics in diluted magnetic semiconductor quantum wells is typically governed by spin-flip scattering processes due to the exciton-impurity exchange interaction. Our theoretical calculations show that the giant Zeeman splitting in these materials in combination with the influence of longitudinal acoustic phonons lead to a quantum ratchet-type dynamics, resulting in an almost complete reversal of the carrier spin polarization at very low temperatures. Furthermore, we find that the predictions of a much simpler rate-equation approach qualitatively agree with a more advanced and numerically demanding quantum kinetic description of the spin dynamics for a wide range of temperatures, although quantitative difference are noticeable.