拓扑绝缘体表面态中的非线性自旋电流
Non-linear spin current in the surface states of topological insulators
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中文总结 AI 辅助
该研究利用守恒自旋输运形式，结合布洛赫态微扰与玻尔兹曼输运方程，探究Bi₂Te₃等拓扑绝缘体表面态的线性与非线性自旋电流，揭示了带几何量对自旋电导率张量分量的选择作用。
中文摘要 AI 辅助
自旋霍尔效应是自旋电子器件中纯自旋电流的主要来源之一，在自旋轨道耦合材料中被观测到。本研究利用守恒自旋输运形式，探究Bi₂Te₃等拓扑绝缘体的六角形扭曲表面态中的线性与非线性纯自旋电流。六角形扭曲效应提供了不破坏时间反演对称性的明确定义的贝里曲率，使该形式得以应用。线性响应中不存在面内自旋电流，因此将该形式扩展至非线性区域，结合布洛赫态微扰与玻尔兹曼输运方程。二阶响应呈现由自旋加权贝里曲率、贝里连接极化率（BCP）偶极子、贝里曲率偶极子（BCD）分别诱导的本征与非本征面内自旋电流。Bi₂Te₃材料的C₃v对称性导致的能带各向异性，通过自旋结构与带几何量传递，最终选择了自旋电导率张量的某些分量。
英文摘要
Spin Hall effect is one of the primary sources of pure spin current in spintronic devices, observed in spin-orbit coupled materials. In this work, we investigate linear and non-linear pure spin currents in the hexagonally warped surface states of topological insulators like $\rm Bi_2Te_3$, using the formalism of conserved spin transport. The hexagonal warping effect enables the application of this formalism by providing a well-defined Berry curvature without breaking the time-reversal symmetry. The absence of in-plane spin currents in the linear response motivates the extension of the formalism to the non-linear regime, by combining the perturbation of Bloch states with the Boltzmann transport equation. The second-order response exhibits both intrinsic and extrinsic in-plane spin currents induced by the spin-weighted Berry curvature, Berry connection polarizability (BCP) dipole and Berry curvature dipole (BCD) respectively. The band anisotropy due to the $C_{3v}$ symmetry of the material ($\rm Bi_2Te_3$) propagates through the spin textures and the band geometric quantities, resulting in the selection of certain components of the spin conductivity tensors.
