New selection rule of resonant Raman scattering in MoS_(2) monolayer under circular polarization

The first-order resonant Raman spectra of monolayer MoS_(2)are calculated under the circularly polarized photoexcitation.The anomalously nonzero Raman intensity of the in-plane E mode under the Z(σ+σ+)Zor Z(σ−σ−)Zgeometry,which goes against the conventional selection rule,appears under some circum-stances when optical absorption occurs at some special reciprocal points between the zone-center Γ and the zone-edge-center M points.At that moment,the valley selectivity to the circular polarization is lifted.The analysis shows that the anomalous Raman intensity of the E mode for the same circularly polarized incident and scattered light is consistent with the pseudo-angular-momentum conservation law.The cal-culated E Raman tensor of monolayer MoS_(2)is found to vary with laser energy.The two diagonal terms of the Raman tensor change their signs from mutually opposite to the same when the relative intensity of the in-plane E mode to the out-of-plane A'_(1)mode increases,indicating the increasingly important role played by the Frölich-type electron-phonon interaction over the deformation potential.Our study may shed new light on the understanding of the novel electron-photon process and assist in the design of new type of optoelectronic devices.