Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 39: Posters II (Topological insulators; Graphene; Spintronics and spin physics; Quantum information science)

HL 39.7: Poster

Tuesday, March 17, 2015, 14:00–20:00, Poster F

Electron dynamics of the topological insulator Sb₂Te₂S — •Anna Sophia Ketterl¹, Thomas Kunze¹, Daniel Przyrembel¹, Dominic Lawrenz^1,3, Evgeny Chulkov², and Martin Weinelt¹ — ¹Freie Universität Berlin, Germany — ²UPV/EHU San Sebastian, Spain — ³Humbold Universität Berlin, Germany

We investigate the electron dynamics of the topological insulator Sb₂Te₂S by means of time-resolved two-photon photoemission measurements with an angle-resolving time-of-flight spectrometer.

Sb₂Te₂S is p-doped and exhibits a Dirac cone 0.3 eV above the Fermi energy at the center of the Brillouin zone. In our experiment, the Dirac cone is populated by an infrared pump-pulse via direct absorption and interband scattering from the conduction band. In the Dirac cone we observe picosecond lifetimes. The spectra hint at a stepwise relaxation via small-energy transfer processes and strong surface-to-bulk coupling. Cooling of the system leads to faster electron dynamics.
The observed dynamics are governed by electron-phonon and defect scattering. Thus our measurements confirm the supercollision model which was proposed for graphene.[1]

Quality and component stoichiometries of the samples were studied by XPS after different preparation methods. We find that Sb₂Te₂S is rather inert and only slowly oxidizes after cleaving under ambient conditions.

[1] J. C. W. Song et. al., Phys. Rev. Let. 109, 106602 (2012).