拓扑绝缘体翘曲表面带内输运引起的非线性反阻尼自旋轨道矩
Non-linear antidamping spin-orbit torque originating from intra-band transport on the warped surface of a topological insulator
摘要：
最近的实验观察到的三维拓扑绝缘体表面上的一个大的反阻尼自旋轨道力矩（SOT）的启发，我们调查的起源电流诱导的SOT超出线性响应理论。我们发现，一个强大的反阻尼SOT产生的带内跃迁的非线性响应，并不需要带间跃迁的情况下，在线性传输机制。翘曲和面内磁化的联合效应产生非线性抗阻尼SOT，其可以超过本征的几个数量级，这取决于翘曲参数和费米能的位置，并表现出复杂的依赖于磁化的方位角。这种非线性的SOT为最近实验中观测到的巨SOT提供了另一种解释。
英文摘要：
Motivated by recent experiments observing a large antidamping spin-orbit torque (SOT) on the surface of a three-dimensional topological insulator, we investigate the origin of the current-induced SOT beyond linear-response theory. We find that a strong antidamping SOT arises from intraband transitions in non-linear response, and does not require interband transitions as is the case in linear transport mechanisms. The joint effect of warping and an in-plane magnetization generates a non-linear antidamping SOT which can exceed the intrinsic one by several orders of magnitude, depending on warping parameter and the position of Fermi energy, and exhibits a complex dependence on the azimuthal angle of the magnetization. This nonlinear SOT provides an alternative explanation of the observed giant SOT in recent experiments.
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