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arXiv 0812.4800cond-mat.mes-hall
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自旋霍尔效应的Boltzmann方法和电场修正的碰撞积分

Boltzmann approach to the spin Hall effect revisited and electric field modified collision integrals

Janik Kailasvuori

摘要:

用量子玻尔兹曼方法研究了非磁性杂质对二维电子气自旋霍尔效应的贡献。结果表明,如果稳态响应是微扰的自旋-轨道耦合参数$λ$,那么旋进项-Dyakonov-Perel松弛和关键的自旋霍尔效应在以前类似的玻尔兹曼研究-必须被排除到一阶的自旋-轨道耦合。在这种情况下,人们将得到,对于参数电场、自旋轨道耦合、杂质强度和杂质浓度的最低阶,不仅对于Rashba耦合,而且对于一般的自旋轨道耦合,对自旋霍尔效应没有本征贡献。为了涵盖所有可能的最低阶项,我们也考虑电场诱导的修正碰撞积分的Keldysh形式主义。然而,这些修正在$λ$中是二阶的。为了比较,我们得出一些熟悉的结果时,响应不被假定为扰动的情况下,在$λ$。我们还包括一个详细的讨论,为什么碰撞积分的弛豫时间近似失败。最后对双层石墨烯中的赝自旋电流进行了评述。

英文摘要:

The intrinsic contribution to the spin Hall effect in a 2DEG with non-magnetic impurities is studied in a quantum Boltzmann approach. It is shown that if the steady state response is perturbative in the spin-orbit coupling parameter $λ$, then the precession term--vital for Dyakonov-Perel relaxation and the key to the spin Hall effect in previous similar Boltzmann studies--must be left out to first order in spin-orbit coupling. In such a case one would have that to lowest order in the parameters electric field, spin-orbit coupling, impurity strength and impurity concentration there is no intrinsic contribution to the spin Hall effect, not only for a Rashba coupling but for a general spin-orbit coupling. To cover all possible lowest order terms we consider also electric field induced corrections to the collision integral in the Keldysh formalism. However, these corrections turn out to be of second order in $λ$. For comparison we derive some familiar results in the case when the response is not assumed to be perturbative in $λ$. We also include a detailed discussion of why a relaxation time approximation of the collision integral fails. Finally we make a comment on pseudospin currents in bilayer graphene.

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