Nonlinear circular valley photogalvanic effect

TL;DR

This paper presents a theoretical study of a nonlinear circular photogalvanic effect in 2D transition metal dichalcogenide monolayers, revealing a second-order intensity effect driven by valley population and carrier drift under specific optical conditions.

Contribution

It introduces a new nonlinear photogalvanic effect in non-gyrotropic 2D materials, expanding understanding of light-matter interactions in valleytronics.

Findings

The effect arises in second intensity order, unlike conventional linear effects.

It depends on valley population by circular in-plane fields.

Carrier drift is induced by linearly polarized in-plane fields with valley asymmetry.

Abstract

We develop a theory of circular photogalvanic effect in non-gyrotropic two-dimensional transition metal dichalcogenide monolayers under interband optical transitions. Oblique incidence of circularly-polarized electromagnetic field or normal incidence of elliptically polarized electromagnetic field is assumed. In contrast to the linear-in-intensity conventional photogalvanic effect, the effect considered here arises in the second intensity order. The effect is conditioned by i) the predominant population of the valleys by the circular in-plane electromagnetic field component and ii) the direct drift of the photo-excited carriers by the linear-polarized in-plane electromagnetic field component in the presence of trigonal valley asymmetry.