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 MoS2, 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 multi-orbital nature of the bands and spin-orbit coupling strongly affects inter-valley scattering processes by gapping certain two-particle modes at large momentum transfer.
@article{arxiv.1601.01707,
title = {Valley Plasmonics in the Dichalcogenides},
author = {R. E. Groenewald and M. Rösner and G. Schönhoff and S. Haas and T. O. Wehling},
journal= {arXiv preprint arXiv:1601.01707},
year = {2016}
}