Dresden 2017 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 67: Topological Insulators II (joint session DS, HL, MA, O, TT, organized by HL)

TT 67.6: Vortrag

Donnerstag, 23. März 2017, 16:30–16:45, POT 251

THz radiation induced helicity sensitive photocurrents in type-II GaSb/InAs quantum well structures — •Helene Plank¹, Johanna Pernul¹, Tanja Hummel¹, Georg Knebl², Pierre Pfeffer², Martin Kamp², Susanne Mueller³, Thomas Tschirky³, Sergey A. Tarasenko⁴, Werner Wegscheider³, Sven Höfling^2,5, and Sergey D. Ganichev¹ — ¹Terahertz Center, University of Regensburg, Regensburg, Germany — ²Technische Physik University of Würzburg, Würzburg, Germany — ³ETH Zurich, Solid State Physics Laboratory, Zurich, Switzerland — ⁴Ioffe Institute, St.Petersburg, Russia — ⁵University of St. Andrews, St. Andrews, United Kingdom

We report on the observation of terahertz radiation induced helicity sensitive photocurrents in GaSb/InAs quantum wells in the inverted regime. The photocurrent reverses its direction upon switching the circular polarization from left- to right-handed. The origin of the photocurrent depends on the experimental geometry and the Fermi energy position. For illuminating the sample centre, it stems from asymmetric scattering of free carriers excited by electric THz field [1]. At normal incidence or for Fermi energies in the gap it vanishes. The situation changes at the sample edges, where is it observed for both cases. We show that this edge current is caused by optical excitation of helical edge states in 2D topological insulators. The observed sign inversion upon changing the photon helicity is attributed to selection rules of optical transitions. We discuss the photocurrent behaviour and present microscopic models. [1] H. Plank et al., Physica E 85, 193 (2017).