Terahertz radiation driven chiral edge currents in graphene

TL;DR

This paper reports the observation of chiral edge photocurrents in graphene induced by circularly polarized terahertz radiation, revealing edge-specific symmetry breaking and potential for characterizing electronic properties.

Contribution

It demonstrates the generation of edge-specific chiral photocurrents in graphene driven by terahertz radiation and provides a theoretical explanation for this phenomenon.

Findings

Photocurrents flow along graphene edges forming vortices.

Reversal of current direction with light helicity.

Edge photocurrents can determine local electronic properties.

Abstract

We observe photocurrents induced in single layer graphene samples by illumination of the graphene edges with circularly polarized terahertz radiation at normal incidence. The photocurrent flows along the sample edges and forms a vortex. Its winding direction reverses by switching the light helicity from left- to right-handed. We demonstrate that the photocurrent stems from the sample edges, which reduce the spatial symmetry and result in an asymmetric scattering of carriers driven by the radiation electric field. The developed theory is in a good agreement with the experiment. We show that the edge photocurrents can be applied for determination of the conductivity type and the momentum scattering time of the charge carriers in the graphene edge vicinity.