Dresden 2020 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 65: Poster Session Topological Topics

TT 65.1: Poster

Donnerstag, 19. März 2020, 15:00–19:00, P2/EG

Quasiparticle interference and spin texture in thin film topological insulator — •Alireza Akbari1,2,3,4 and Peter Thalmeier31Max Planck POSTECH Center for Complex Phase Materials, POSTECH, Pohang 790-784, Korea — 2Asia Pacific Center for Theoretical Physics, POSTECH, Pohang, Korea — 3Max Planck Institute for Chemical Physics of Solids, Dresden, Germany — 4Department of Physics, POSTECH, Pohang, Korea

The protected surface states of topological insulators (TI) form gapless Dirac cones corresponding non-degenerate eigenstates with helical spin polarization. The presence of a warping term deforms the isotropic cone of the most simple model into snowflake Fermi surfaces as in Bi2Se3 and Bi2Te3. Their features have been identified in STM quasiparticle interference (QPI) experiments on isolated surfaces. Here we investigate the QPI spectrum for the TI thin film geometry with a finite tunneling between the surface states. This leads to a dramatic change of spectrum due to gapping and a change in pseudo spin texture that should leave distinct signatures in the QPI pattern. We consider both normal and magnetic exchange scattering from the surface impurities and obtain the scattering t-matrix in Born approximation as well as the general closed solution. We show the expected systematic variation of QPI ‘snowflake’ features by varying film thickness and study in particular the influence on back scattering processes. We show that a closing of the gap at special thickness due nonmonotonic tunneling matrix element should be visible in QPI.

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