Nonlinear circular valley photogalvanic effect

We develop a theory of circular photogalvanic effect in nongyrotropic 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 photoexcited carriers by the linear-polarized in-plane electromagnetic field component in the presence of trigonal valley asymmetry.