Spin scattering of topologically protected electrons at defects

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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).