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arXiv 0807.0771cond-mat.mes-hall
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量子阱中子带间诱导的自旋轨道相互作用

Intersubband-induced spin-orbit interaction in quantum wells

Rafael S. Calsaverini, Esmerindo Bernardes, J. Carlos Egues, Daniel Loss

摘要:

最近,我们发现了一个额外的自旋轨道(SO)相互作用的量子阱中的两个子带[物理评论Lett。99,076603(2007)]。这个新的SO项是非零的,即使在对称的几何形状,因为它产生于不同的宇称的受限状态之间的子带间耦合,其强度是普通的Rashba。本文从$8 \times 8$ Kane模型出发,详细推导了这种新的SO哈密顿量和相应的SO耦合。此外,在自洽的Hartree近似下,我们计算了这种新的SO耦合的强度为现实的对称调制掺杂阱与两个子带。我们考虑具有恒定面电子密度或恒定化学势的门控结构。在所研究的参数范围内,两种模型给出了相似的结果。通过考虑外部施加的偏置,这打破了结构反转对称的井的影响,我们还计算了每个子带内产生的诱导Rashba耦合的强度。有趣的是,我们发现,对于双阱的Rashba耦合的第一和第二子带交换符号突然跨越零偏置,而子带间SO耦合表现出这种对称配置附近的共振行为。为了完整性,我们还确定的Dresselhaus耦合的强度,并发现它们基本上是恒定的所施加的偏压的函数。

英文摘要:

Recently, we have found an additional spin-orbit (SO) interaction in quantum wells with two subbands [Phys. Rev. Lett. 99, 076603 (2007)]. This new SO term is non-zero even in symmetric geometries, as it arises from the intersubband coupling between confined states of distinct parities, and its strength is comparable to that of the ordinary Rashba. Starting from the $8 \times 8$ Kane model, here we present a detailed derivation of this new SO Hamiltonian and the corresponding SO coupling. In addition, within the self-consistent Hartree approximation, we calculate the strength of this new SO coupling for realistic symmetric modulation-doped wells with two subbands. We consider gated structures with either a constant areal electron density or a constant chemical potential. In the parameter range studied, both models give similar results. By considering the effects of an external applied bias, which breaks the structural inversion symmetry of the wells, we also calculate the strength of the resulting induced Rashba couplings within each subband. Interestingly, we find that for double wells the Rashba couplings for the first and second subbands interchange signs abruptly across the zero bias, while the intersubband SO coupling exhibits a resonant behavior near this symmetric configuration. For completeness we also determine the strength of the Dresselhaus couplings and find them essentially constant as function of the applied bias.

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