Spectroscopic insight into current-induced spin-transfer torques in ferromagnet/topological insulator interfaces

计划研究的目标是描述包含3D拓扑绝缘体（3D TI）和金属铁磁体（FM）或绝缘铁磁体（FMI）的双层异质结构中电流诱导自旋力矩的电子结构起源。此外，将进行由磁性薄膜的接近在3D TI中引起的交换分裂的光谱分析。据设想，计划中的研究计划将允许演示电流诱导的自旋扭矩在EuO/TI FMI/TI系统的自旋极化角分辨光电发射（spinARPES）。这将允许解决的争议，电流引起的扭矩占主导地位的FM/TI和FMI/TI结构的机制：螺旋锁定的狄拉克锥电子或Rashba或自旋霍尔效应扭矩由于不对称的接口。这些目标将通过使用新开发的接触阶段来实现，该阶段允许向样品施加电流或与光电发射测量同时原位测量其电阻。这种实验设置将允许结合两种典型的不同方法：传输测量和高分辨率光电子能谱，并有可能额外测量光致表面电流，例如由于光电流或光子拖曳效应。这些异质结构的界面电子结构将通过spinARPES和其他常规表面科学技术如XPS和LEED来表征。这些异质结构的基本磁阻测量将在原位同时进行spinARPES测量。

The goal of the planned research is to describe the electronic structure origin of the current-induced spin torque in the bilayer heterostructures containing the 3D topological insulator (3D TI) and the metallic ferromagnet (FM) or insulating ferromagnet (FMI). Further, a spectroscopic analysis of exchange splitting induced in the 3D TI by the proximity of the magnetic thin film will be carried out. It is envisioned that the planned research program will allow demonstrating current induced spin torques in the EuO/TI FMI/TI system by spin-polarized angle-resolved photoemission (spinARPES). This will allow resolving the controversy which mechanism of the current induced torque dominates in the FM/TI and FMI/TI structures: the helical locking of the Dirac cone electrons or the Rashba or spin-Hall effect torques due to the asymmetric interface. These goals will be achieved by the use of the newly developed contact stage which allows applying the current to the sample or measuring its resistance in-situ simultaneously with photoemission measurements. This experimental setup will allow combining the two typically distinct approaches: transport measurements and high-resolution photoelectron spectroscopy, with the possibility to additionally measure optically induced surface currents for example due to the photogalvanic or photon drag effects. Interface electronic structure of these heterostructures will be characterized by spinARPES and other routine surface science techniques such as XPS and LEED. Basic magnetoresistance measurements of these heterostructures will be performed in-situ simultaneously with spinARPES measurements.