Helicity-dependent photocurrents in graphene layers excited by mid-infrared radiation of a CO$_2$-laser

Chongyun Jiang, V. A. Shalygin, V. Yu. Panevin, S. N. Danilov, M. M. Glazov, R. Yakimova, S. Lara-Avila, S. Kubatkin, S. D. Ganichev

Published 2011-05-31Version 1

We report the study of the helicity driven photocurrents in graphene excited by mid-infrared light of a CO$_2$-laser. Illuminating an unbiased monolayer sheet of graphene with circularly polarized radiation generates -- under oblique incidence -- an electric current perpendicular to the plane of incidence, whose sign is reversed by switching the radiation helicity. We show that the current is caused by the interplay of the circular $ac$ Hall effect and the circular photogalvanic effect. Studying the frequency dependence of the current in graphene layers grown on the SiC substrate we observe that the current exhibits a resonance at frequencies matching the longitudinal optical phonon in SiC.