Dresden 2017 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 76: Topological Insulators II (joined session with TT)

HL 76.6: 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 Höfling2,5, and Sergey D. Ganichev11Terahertz 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).

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