Inverse spin Hall effect induced by asymmetric illumination of light in topological insulator Bi_{2}Se_{3}

Abstract

Illumination of circularly polarized light is an alternative to electrical methods for spin injection. Spins are injected at the point of light illumination, and then they diffuse radially due to the in-plane gradient of the spin density. This diffusing spin current is converted into a circular charge current by the inverse spin Hall effect (ISHE) and is usually not detectable. However, by shining a light on an asymmetric part of the sample, such as near the edges, we detected this current as a helicity-dependent component in the measured photocurrent. This is not due to the circular photogalvanic effect because it occurs even at normal incidence of the light. A finite-element-method simulation shows that the ISHE-induced circular charge current generates an electric dipole at the edge of the sample, causing the measured charge current. The asymmetric light illumination shown here is a simple way to control the output of the ISHE, which may lead to novel spintronic devices.