论文标题
拓扑表面状态渗透引起的自旋扭矩和持续电流
Spin torque and persistent currents caused by percolation of topological surface states
论文作者
论文摘要
拓扑绝缘子/铁磁金属（TI/FMM）双层薄膜出现为有前途的拓扑表面状态旋转器设备，最著名的是它们的电流诱导的自旋扭矩效率。使用立方晶格模型，我们揭示了Ti的表面状态狄拉克锥可以逐渐合并到或与FMM散装带高度交织在一起，并且表面状态渗透到FMM中，并最终与其中的量子井状态杂交。磁化强度会扭曲表面状态的自旋摩肌锁定，并产生不对称的带结构，从而导致室温持续电荷电流的层流。此外，与FMM的接近性还促进了持续的层流旋转电流。通过线性响应理论，我们阐述了表面状态和FMM散装带有助于电流诱导的自旋扭矩，其真实波函数使自旋扭矩主要类似场状，并且受表面状态渗透程度的高度影响。另一方面，杂质可以改变Edelstein效应预期的自旋极化，并产生阻尼状的扭矩，即使磁化强度指向平面内和正交到电流方向，也会产生扭矩。
The topological insulator/ferromagnetic metal (TI/FMM) bilayer thin films emerged as promising topological surface state-based spintronic devices, most notably in their efficiency of current-induced spin torque. Using a cubic lattice model, we reveal that the surface state Dirac cone of the TI can gradually merge into or be highly intertwined with the FMM bulk bands, and the surface states percolate into the FMM and eventually hybridize with the quantum well states therein. The magnetization can distort the spin-momentum locking of the surface states and yield an asymmetric band structure, which causes a laminar flow of room temperature persistent charge current. Moreover, the proximity to the FMM also promotes a persistent laminar spin current. Through a linear response theory, we elaborate that both the surface state and the FMM bulk bands contribute to the current-induced spin torque, and their real wave functions render the spin torque predominantly field-like, with a magnitude highly influenced by the degree of the percolation of the surface states. On the other hand, impurities can change the spin polarization expected from the Edelstein effect and generate a damping-like torque, and produce a torque even when the magnetization points in-plane and orthogonal to the current direction.
