Zheng Shi-Han, Duan Hou-Jian, Yang Mou, Hu Liang-Bin, Wang Rui-Qiang
Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Material, ICMP and SPTE, South China Normal University, Guangzhou 510006, People's Republic of China.
J Phys Condens Matter. 2018 Aug 22;30(33):335404. doi: 10.1088/1361-648X/aad218. Epub 2018 Jul 9.
We provide a general transport theory for spin-polarized scanning tunneling microscopy (STM) through a doped topological insulator (TI) surface. It is found that different from the conventional magnetic substrate, the tunneling conductance through the tip-TI surface acquires an extra component determined by the in-plane spin texture, exclusively associated with the spin momentum locking. Importantly, this extra conductance unconventionally depends on the spatial azimuthal angle of the magnetized STM tip. By introducing a magnetic impurity to break the symmetry of rotation and local time reversal of the TI surface, we find that the measurement of the spatial resolved conductance can reconstruct the helical structure of spin texture, from which the spin-momentum locking angle can be extracted if the in-plane magnetization is induced purely by the spin-orbit coupling of surface Dirac electrons. Our theory offers an alternative way, differing from existing in-plane-current polarization probed in a multi-terminal setup or angle resolved photoemission spectroscopy, to electrically identify the helical spin texture on TI surfaces.
我们提出了一种通过掺杂拓扑绝缘体（TI）表面的自旋极化扫描隧道显微镜（STM）的通用输运理论。研究发现，与传统磁性衬底不同，通过针尖-TI表面的隧穿电导获得了一个由面内自旋纹理决定的额外分量，该分量专门与自旋动量锁定相关。重要的是，这种额外的电导反常地依赖于磁化STM针尖的空间方位角。通过引入磁性杂质来打破TI表面的旋转对称性和局部时间反演对称性，我们发现空间分辨电导的测量可以重建自旋纹理的螺旋结构，如果面内磁化纯粹由表面狄拉克电子的自旋轨道耦合诱导，则可以从中提取自旋动量锁定角。我们的理论提供了一种不同于现有在多端设置中探测面内电流极化或角分辨光电子能谱的方法，用于电识别TI表面上的螺旋自旋纹理。
