量子自旋霍尔态的持续电流和自旋矩
Persistent currents and spin torque caused by percolated quantum spin Hall state
摘要：
受最近实验的启发，我们利用紧束缚模型和线性响应理论研究了二维拓扑绝缘体/铁磁金属平面结中的量子自旋霍尔态.我们证明了边缘态狄拉克锥是否淹没在铁磁子带中以及磁化方向对边缘态如何进入铁磁子带以及边缘态的自旋-动量锁定有显著的影响。揭示了界面附近的室温持续电荷流和自旋流的层流。此外，发现在2D拓扑绝缘体的边缘处的电流诱导自旋极化在杂质附近显著增强。铁磁体中的电流诱导自旋极化主要在平面外方向${\hat{\bf z}}$上极化，从而呈现主要为类场$\propto {\bf S}\times{\hat{\bf z}}$的电流诱导自旋扭矩。
英文摘要：
Motivated by recent experiments, we investigate the quantum spin Hall state in 2D topological insulator/ferromagnetic metal planar junctions by means of a tight-binding model and linear response theory. We demonstrate that whether the edge state Dirac cone is submerged into the ferromagnetic subbands and the direction of the magnetization dramatically affect (i) how the edge state percolates into the ferromagnet, and (ii) the spin-momentum locking of the edge state. Laminar flows of room temperature persistent charge and spin currents near the interface are uncovered. In addition, the current-induced spin polarization at the edge of the 2D topological insulator is found to be dramatically enhanced near the impurities. The current-induced spin polarization in the ferromagnet is mainly polarized in the out-of-plane direction ${\hat{\bf z}}$, rendering a current-induced spin torque that is predominantly field-like $\propto {\bf S}\times{\hat{\bf z}}$.
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