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arXiv 1609.02582cond-mat.mes-hall
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非磁性杂质散射对稀磁半导体自旋动力学的影响

Influence of non-magnetic impurity scattering on the spin dynamics in diluted magnetic semiconductors

Moritz Cygorek, Florian Ungar, Pablo Ignacio Tamborenea, Vollrath Martin Axt

摘要:

半导体中磁性杂质的掺杂不仅引起准自由载流子和磁性杂质之间的自旋-自旋相互作用,而且引起载流子的局部自旋无关的无序势。基于载流子和杂质密度矩阵的量子动力学理论以及磁性和非磁性载流子-杂质关联,以Mn掺杂的CdTe为例,研究了非磁性散射势对圆偏振光激发后DMS自旋动力学的影响.结果表明,非马尔可夫效应,这是预测在计算中,只有磁性载流子-杂质相互作用占,可以强烈抑制在非磁性杂质散射的存在下。这种效应可以追溯到一个显着的重新分布的载流子在$\mathbf{k}$ -空间,这是使大的载流子杂质相关能量的积累。与量子动力学理论的马尔可夫极限的比较表明,在平行于初始载流子极化方向的外部磁场存在下,量子动力学和马尔可夫极限计算的自旋极化的长时间渐近值有显著的不同.这种效应也可以归因于强相关性的形成,使半经典马尔可夫图失效,并且当考虑非磁性载流子-杂质相互作用时,这种效应更强。在垂直于初始载流子自旋的外部磁场中,相关性也负责载流子自旋进动频率的重整化。

英文摘要:

The doping of semiconductors with magnetic impurities gives rise not only to a spin-spin interaction between quasi-free carriers and magnetic impurities, but also to a local spin-independent disorder potential for the carriers. Based on a quantum kinetic theory for the carrier and impurity density matrices as well as the magnetic and non-magnetic carrier-impurity correlations, the influence of the non-magnetic scattering potential on the spin dynamics in DMS after optical excitation with circularly polarized light is investigated using the example of Mn-doped CdTe. It is shown that non-Markovian effects, which are predicted in calculations where only the magnetic carrier-impurity interaction is accounted for, can be strongly suppressed in the presence of non-magnetic impurity scattering. This effect can be traced back to a significant redistribution of carriers in $\mathbf{k}$-space which is enabled by the build-up of large carrier-impurity correlation energies. A comparison with the Markov limit of the quantum kinetic theory shows that, in the presence of an external magnetic field parallel to the initial carrier polarization, the asymptotic value of the spin polarization at long times is significantly different in the quantum kinetic and the Markovian calculations. This effect can also be attributed to the formation of strong correlations which invalidates the semiclassical Markovian picture and it is stronger when the non-magnetic carrier-impurity interaction is accounted for. In an external magnetic field perpendicular to the initial carrier spin, the correlations are also responsible for a renormalization of the carrier spin precession frequency.

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