Dresden 2014 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 27: Topological Insulators: Mostly Interaction with Magnetic Fields (organized by HL)

TT 27.6: Talk

Monday, March 31, 2014, 17:00–17:15, POT 081

Giant Photocurrents in a Dirac Fermion System at Cyclotron Resonance — •C. Zoth¹, P. Olbrich¹, P. Vierling¹, K.-M. Dantscher¹, G.V. Budkin², S.A. Tarasenko², V.V. Bel’kov², D.A. Kozlov³, Z.D. Kvon³, N.N. Mikhailov³, S.A. Dvoretsky³, and S.D. Ganichev¹ — ¹Terahertz Center, Regensburg, Germany — ²Ioffe Institute, St. Petersburg, Russia — ³Institute of Semiconductor Physics, Novosibirsk, Russia

We report on the observation of giant photocurrents in HgTe/HgCdTe quantum wells (QW) of critical thickness at which a Dirac spectrum emerges [1]. Exciting QW of 6.6 nm width by terahertz radiation and varying an external magnetic field we detected a resonant photocurrent. Remarkably, the position of the resonance can be tuned from negative (-0.4 T) to positive (up to 1.2 T) magnetic fields by means of optical doping. The photocurrent data, accompanied by measurements of radiation transmission, as well as, magnetotransport, prove that the photocurrent is caused by cyclotron resonance in a Dirac fermion system. This allows us to obtain the effective electron velocity v ≈ 7.2 × 10⁵ m/s. We develop a microscopic theory of the effect and show that the inherent spin-dependent asymmetry of light-matter coupling in the system of Dirac fermions causes the electric current to flow.
[1] P. Olbrich, C. Zoth, P. Vierling et al., PRB 87, 235439 (2013)