Dresden 2014 – scientific programme
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MA: Fachverband Magnetismus
MA 12: Topological insulators: mostly interaction with magnetic fields (with HL/O/TT)
MA 12.6: 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)