Tailoring the spin-orbit interaction at surfaces and interfaces

自旋-轨道相互作用在许多不同的领域中扮演着重要的角色，例如用于分离自旋态的自旋电子学，而不需要使用磁场或本征的自旋霍尔效应。然而，许多基本原理，特别是强自旋分离的设计标准，仍有待理解。这一建议旨在设计和研究低维电子系统中表面和界面的自旋-轨道耦合引起的自旋分裂能带。在他的博士后研究期间，申请人发现了一种新的材料，它基于通过高Z元素掺杂进行表面合金化的概念，其中表面的二维能带结构显示出极强的自旋分裂。再加上表面合金化的设计灵活性，这为继续研究开辟了良好的前景。利用角度分辨光电子能谱(ARPES)和扫描隧道显微镜/光谱学(STM/STS)这两种互补性很强的技术，我们将研究金属和半导体衬底上具有强自旋分裂能带结构的新系统的基本机制和设计可能性。此外，预计将对电子相互作用进行修正。此外，申请人还首次证明，自旋分裂可以通过STS的差示电导光谱来定量地评估。这一在局部尺度上探测自旋分裂的新途径也将在这项提议中进行探索。结合表面合金化的设计灵活性，它为研究自旋分裂梯度提供了可能。从长远来看，将利用克尔显微镜设计一个实验来探索这些系统的本征自旋霍尔效应，并测试最近提出的本征自旋霍尔电导率的普适性。

The spin-orbit interaction plays an important role in many different areas, such as spintronics for separating spin states without the use of magnetic fields or the intrinsic spin Hall effect. However, much of the fundamentals, especially design criteria for a strong spin separation, remain to be understood. This proposal aims at the design and study of spin-split energy bands induced by spin-orbit coupling in low-dimensional electron systems at surfaces and interfaces. During his postdoctoral studies the applicant has found a new class of materials based on the concept of surface alloying by means of high-Z element doping, where the two-dimensional band structure at the surface exhibits an extremely strong spin-splitting. Together with the design flexibility of surface alloying, this opens up excellent prospects for continuing research. Using the two very complementary techniques angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy/spectroscopy (STM/STS), the underlying mechanism and the design possibilities of new systems with a strongly spin-split band structure on metallic as well as semiconducting substrates will be studied. In addition, corrections to electronic interactions are expected. Furthermore, the applicant has shown for the first time that the spin-splitting can be evaluated quantitatively from differential conductance spectra by STS. This new avenue of detecting the spin-splitting on a local scale will also be explored within this proposal. In combination with the design flexibility of surface alloying, it opens up the possibility to study spin-splitting gradients. In the long term, an experiment will be devised using Kerr microscopy to probe these systems for the intrinsic spin Hall effect and test the recently proposed universality of the intrinsic spin Hall conductivity.