Valley plasmonics in transition metal dichalcogenides

Abstract

The rich phenomenology of plasmonic excitations in the dichalcogenides is analyzed as a function of doping. The many-body polarization, the dielectric response function, and electron energy loss spectra are calculated using an ab initio based model involving material-realistic Coulomb interactions, band structure, and spin-orbit coupling. Focusing on the representative case of ${\mathrm{MoS}}_{2}$, a plethora of plasmon bands are observed, originating from scattering processes within and between the conduction or valence band valleys. We discuss the resulting square-root and linear collective modes, arising from long-range versus short-range screening of the Coulomb potential. We show that the multiorbital nature of the bands and spin-orbit coupling strongly affects intervalley scattering processes by gapping certain two-particle modes at large momentum transfer.