Spin scattering of topologically protected electrons at defects

拓扑绝缘体(TI)领域正朝着两个方向发展：发现具有新拓扑概念的新材料，如Weyl半金属；或在已知和研究的材料中应用。目前的提议包括后一方向的主题，重点是输运现象和自旋-电荷转换：Edelstein(磁电)效应、自旋轨道扭矩、自旋泵浦、反常霍尔效应和对TI的电势测量。输运现象总是与耗散和位相退相干效应有关。在电荷或自旋输运过程中，一个普遍存在的耗散来源是杂质原子和其他缺陷的散射。我们从第一个资助期获得的关于杂质散射的经验将在这里得到应用。我们关于Bi2Te3中聚焦效应的发现，关于通过费米面嵌套的后向散射的可能性，或者关于通过掺杂改变费米面对散射性质的塑造，所有这些都是丰富和潜在的应用以及在TI上定制输运性质的例子。借助于玻尔兹曼型方程，我们将从从头计算的散射幅度和能带结构入手，系统地研究其潜在的应用，并给出实验指导。在社区中获得的经验表明，最流行的三维TI，Bi2Te3和Bi2Se3，可以用密度泛函理论很好地描述，因此我们对我们的方法有信心。同时，我们将继续把我们方法的核心，即散射幅度，通过将准粒子干涉图案和电位法计算与我们的实验同事(P.Sessi/M.Bode，Y.Ando，C.Bobisch，B.Voigtländer)的结果进行比较来测试和实验。

The field of Topological Insulators (TI) is growing in two directions: discovery of new materials with new topological concepts, e.g. Weyl semimetals, or applications in already known and investigated materials. The present proposal comprises topics in the latter direction with emphasis in transport phenomena and spin-charge conversion: Edelstein (magnetoelectric) effect, spin-orbit torque, spin pumping, anomalous Hall effect, and potentiometry on TI. Transport phenomena are always related to dissipation and phase decoherence effects. A ubiquitous source of dissipation during charge or spin transport is scattering off impurity atoms and other defects. Our gained experience on impurity scattering from the first funding period will be applied here.Our findings on the focussing effect in Bi2Te3, on the possibility of back-scattering via the Fermi Surface nesting, or on the shaping of the scattering properties by changing the Fermi surface via doping, all these are examples of the richness and potential for applications and for tailoring transport properties on TI. By means of Boltzmann-type equations, where the ab-initio-calculated scattering amplitude and band-structure enter, we will systematically investigate prospective applications and give guidelines to experiment. Experience gained in the community shows that the most popular three-dimensional TI, Bi2Te3 and Bi2Se3, are well described by density-functional theory, and therefore we have confidence in our approach. At the same time we will continue to bring the core of our method, i.e. the scatering amplitude, to test versus the experiment by comparing quasiparticle interference patterns and potentiometry calculations with the results of our experimental colleagues (P. Sessi/M. Bode, Y. Ando, C. Bobisch, B. Voigtländer).