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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 Lawrenz1,3, Evgeny Chulkov2, and Martin Weinelt11Freie 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).

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