Regensburg 2019 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 3: Topological Insulators (joint session TT/MA)
TT 3.4: Talk
Monday, April 1, 2019, 10:15–10:30, Theater
Quasiparticle interference and spin momentum locking of topological insulator surface states — •Henry Legg1, Wouter Jolie2, Timo Knispel2, Nick Borgwardt2, Zhiwei Wang2, Markus Grüninger2, Yoichi Ando2, Thomas Michely2, and Carsten Busse2 — 1Institut für Theoretische Physik, Universität zu Köln, Germany — 2II. Physikalisches Institut, Universität zu Köln, Germany
In a normal Schrödinger material, with quadratic dispersion, the Fourier-transform of an STM quasi-particle interference (QPI) image is strongly enhanced close to momenta corresponding to 2kF back-scattering. In constrast, the surface states of 3D topological insulators are protected from back-scattering due to spin-momentum locking and this protection suppresses the otherwise divergent QPI signal at 2kF.
Performing a self-consistent T-matrix calculation for several different scattering potentials, we demonstrate that spin-momentum locking leads to only a smooth dependence of QPI intensity as function of momentum, in particular no sharp features occur close to 2kF.
Our theory will be quantatively compared to measurements on compensated BiSbTeSe2 allowing us to perform a detailed and precise characterisation of the topological insulator surface by extracting the full dispersion, scattering rates, and screening length of charged impurities. Intriguingly the experimental QPI intensity close to 2kF shows a slight deviation from that expected due to perfect protection from backscattering, we will discuss the potential scattering mechanism that results in this effect.