Berlin 2015 – scientific programme
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O: Fachverband Oberflächenphysik
O 61: Topological Insulators: Structure and Electronic Structure (HL with DS/MA/O/TT)
O 61.4: Talk
Wednesday, March 18, 2015, 15:45–16:00, ER 270
Cyclotron Resonance Induced Spin Polarized Photocurrents in Surface States of a 3D Topological Insulator — •K.-M. Dantscher1, D.A. Kozlov2, Z.D. Kvon2, P. Faltermeier1, M. Lindner1, P. Olbrich1, C. Zoth1, G.V. Budkin3, S.A. Tarasenko3, V.V. Bel'kov3, N.N. Mikhailov2, S.A. Dvoretskii2, D. Weiss1, and S.D. Ganichev1 — 1University of Regensburg, Regensburg, Germany — 2Institute of Semiconductor Physics, Novosibirsk, Russia — 3Ioffe Institute, St. Petersburg, Russia
We report on the observation of cyclotron resonance (CR) induced photocurrents excited by cw radiation, with frequencies of 2.54, 1.62 and 0.69 THz in a 3D topological insulator based on 80 nm strained HgTe films. To support the complex study, including optical, optoelectronic and electron transport experiments, various sample designs have been used. The measurements were done in a wide range of temperatures (1.6 to 120 K). We demonstrate that the photocurrent is generated in the topologically protected surface states. Studying the resonance response in the gated samples we examined the behaviour of the photocurrent and Dirac fermions cyclotron mass upon variation of Fermi energy. For large gate voltages we also detected CR in the bulk HgTe with the mass about two times larger than that obtained for the surface states. Based on this data we develop a microscopic theory of the effects and show that the asymmetry of light-matter coupling in the system of Dirac fermions subjected to an external magnetic field causes the electric current to flow. We show that the current is spin polarized.