Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 46: Electronic Structure of Surfaces: Spectroscopy, Surface States

O 46.17: Poster

Dienstag, 21. März 2017, 18:30–20:30, P1A

Polarization-dependent two-photon photoemission from p-doped topological insulators SnBi_xSb_2−xTe4 and GeSb₂Te₄ — •Sebastian Otto, Jonas Rietsch, Philipp Rosenzweig, Daniel Niesner, and Thomas Fauster — Lehrstuhl für Festkörperphysik, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91058 Erlangen, Germany

Polarization-dependent, time- and angle-resolved two-photon photoemission is used to study the electronic structure of septuple-layered antimony telluride crystals of different p-dopings. All surfaces show a linearly dispersing surface state bridging the band gap with a Dirac point at E_F + 0.42 ± 0.05 eV for GeSb₂Te₄ and E_F + 0.31 ± 0.02 eV for the SnBi_xSb_2−xTe₄ crystals. The Bi-doping of the SnBi_xSb_2−xTe₄ (with x=0,0.1,0.2) causes no shift of the energetic position of the Dirac point, but a decrease in group velocity which is reflected in the dynamics of the systems. The lifetimes of the topological surface states range from 10±5 fs to 120 ±20 fs and time constants of the conduction band minimum are found between 180±10 fs and 300±20 fs. Measurements with circularly polarized probe pulses verify the topological nature of the surface states. The excitation of the topological surface state shows no dependence on the polarization of the pump pulse.