title: Ultrafast helicity control of surface currents in topological insulators with near-unity fidelity.
abstract: In recent years, a class of solid-state materials, called three-dimensional topological insulators, has emerged. In the bulk, a topological insulator behaves like an ordinary insulator with a band gap. At the surface, conducting gapless states exist showing remarkable properties such as helical Dirac dispersion and suppression of backscattering of spin-polarized charge carriers. The characterization and control of the surface states via transport experiments is often hindered by residual bulk contributions. Here we show that surface currents in Bi2Se3 can be controlled by circularly polarized light on a picosecond timescale with a fidelity near unity even at room temperature. We reveal the temporal separation of such ultrafast helicity-dependent surface currents from photo-induced thermoelectric and drift currents in the bulk. Our results uncover the functionality of ultrafast optoelectronic devices based on surface currents in topological insulators.
authors: 1] Walter Schottky Institut and Physik-Department, Technische Universität München, Am Coulombwall 4a, 85748 Garching, Germany [2] Nanosystems Initiative Munich (NIM), Schellingstr. 4, 80799 München, Germany.
authors: Christoph
authors: C
authors: Kastl
authors: 1] Walter Schottky Institut and Physik-Department, Technische Universität München, Am Coulombwall 4a, 85748 Garching, Germany [2] Nanosystems Initiative Munich (NIM), Schellingstr. 4, 80799 München, Germany.
authors: Christoph
authors: C
authors: Karnetzky
authors: Institute of Physics, University of Augsburg, 86135 Augsburg, Germany.
authors: Helmut
authors: H
authors: Karl
authors: 1] Walter Schottky Institut and Physik-Department, Technische Universität München, Am Coulombwall 4a, 85748 Garching, Germany [2] Nanosystems Initiative Munich (NIM), Schellingstr. 4, 80799 München, Germany.
authors: Alexander W
authors: AW
authors: Holleitner