Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 80: Surface Dynamics I

O 80.7: Vortrag

Donnerstag, 3. April 2014, 17:30–17:45, GER 38

Bulk- and surface electron dynamics in a p-type topological insulator SnSb₂Te₄ — •Sebastian Otto, Daniel Niesner, Volker Hermann, and Thomas Fauster — Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany

Time-resolved two-photon photoemission is used to study the electronic structure and dynamics at the surface of SnSb₂Te₄, a p-type topological insulator. The topological surface state is centered at 0.32±0.03 eV above the Fermi level with a group velocity of 3.4 eVÅ. Electrons from the conduction band minimum are scattered on a time scale of 43±4 fs to the Dirac cone. From there they decay to the partly depleted valence band with a time constant of 78±5 fs. The short time scales are attributed to the large overlap with the bulk bands. Higher doped samples show even shorter time constants indicating that the unoccupied bulk valence band provides the final states for decay. The infrared-pumped scattering processes above the Dirac cone in the conduction band are described by a rate equation model. States are populated by the pump pulse and electrons decaying from higher-lying states and decay into lower-lying states. The good agreement between filling and depleting decay rates of neighboring energy levels shows that the decay occurs mostly within the conduction band.