Berlin 2018 – scientific programme

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MA: Fachverband Magnetismus

MA 52: Poster II

MA 52.59: Poster

Thursday, March 15, 2018, 15:00–18:00, Poster C

Impact of ultrafast transport on the high-energy states of a photoexcited topological insulator — •Friedrich Freyse¹, Marco Battiato², Andrei Varykhalov¹, Oliver Rader¹, and Jaime Sánchez-Barriga¹ — ¹Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Str. 15, 12489 Berlin, Germany — ²Institute of Solid State Physics, Vienna University of Technology, Vienna A-1040, Austria

Ultrafast dynamics in three-dimensional topological insulators (TIs) opens new routes for increasing the speed of information transport up to frequencies thousand times faster than in modern electronics. However, up to date, disentangling the exact contributions from bulk and surface transport in the subpicosecond dynamics of these materials remains a difficult challenge. Here, using time- and angle-resolved photoemission, we demonstrate that driving a TI into the bulk insulating regime opens new channels for ultrafast transport on the surface that unexpectedly persist up to high energies above the Fermi level. In particular, we show that the emergent transport channels are due to an ultrafast process of surface charge accumulation that is directly connected to the existence of a projected bulk band gap at high energy and the lack of available bulk states at the Fermi level. We further provide a qualitative description of the mechanisms responsible for the observed electron dynamics.