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首页> 外文期刊>Physical review >Trend reversal in the magnetic-field dependence of exciton spin-transfer rates in diluted magnetic semiconductors due to non-Markovian dynamics
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Trend reversal in the magnetic-field dependence of exciton spin-transfer rates in diluted magnetic semiconductors due to non-Markovian dynamics

机译：非马氏动力学导致稀磁半导体中激子自旋转移速率对磁场的趋势逆转

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摘要

We investigate theoretically the influence of an external magnetic field on the spin dynamics of excitons in diluted magnetic semiconductor quantum wells. To this end, we apply a quantum kinetic theory beyond the Markov approximation which reveals that non-Markovian effects can significantly influence the exciton spin dynamics. If the magnetic field is oriented parallel to the growth direction of the well, the Markovian spin-transfer rate decreases monotonically with increasing field as predicted by Fermi's golden rule. The quantum kinetic theory follows this result qualitatively but predicts pronounced quantitative differences in the spin-transfer rate as well as in the long-time spin polarization. However, for an in-plane magnetic field, where the Markovian spin-transfer rate first drops and then increases again, quantum kinetic effects become so pronounced that the Markovian trend is completely reversed. This is made evident by a distinct maximum of the rate followed by a monotonic decrease. The deviations can be traced back to a redistribution of carriers in energy space caused by correlations between excitons and magnetic dopants. The same effect leads to a finite electron-spin polarization at long times in longitudinal as well as transverse fields which is much larger than the corresponding Markovian prediction.
机译：我们从理论上研究外部磁场对稀释磁半导体量子阱中激子自旋动力学的影响。为此，我们应用了超越马尔可夫近似的量子动力学理论，揭示了非马尔可夫效应会显着影响激子自旋动力学。如果磁场的方向平行于井的生长方向，则如费米黄金定律所预测的那样，随着电场的增加，马尔可夫自旋转移速率会单调降低。量子动力学理论定性地遵循了这一结果，但预测了自旋转移速率以及长期自旋极化方面的明显定量差异。但是，对于平面内磁场，马尔可夫自旋传递速率先下降然后再增加，量子动力学效应变得如此明显，以至于马尔可夫趋势被完全逆转。速率的明显最大值随后是单调下降，这证明了这一点。偏差可以追溯到由于激子和磁性掺杂物之间的相关性引起的载流子在能量空间中的重新分布。相同的效果会在纵向和横向场中长时间产生有限的电子自旋极化，远大于相应的马尔可夫预测。

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  • 来源
    《Physical review》 |2018年第4期|045210.1-045210.15|共15页
  • 作者

    F. Ungar; M. Cygorek; V. M. Axt;

  • 作者单位

    Theoretische Physik III, Universitdt Bayreuth, 95440 Bayreuth, Germany;

    Theoretische Physik III, Universitdt Bayreuth, 95440 Bayreuth, Germany;

    Theoretische Physik III, Universitdt Bayreuth, 95440 Bayreuth, Germany;

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