We combine electron energy-loss spectroscopy (EELS) and density functional theory (DFT) calculations to study the dispersion and effective mass of excitons in the bulk of WSe2. Our EELS data suggest substantial deviations from the generic quadratic momentum dependence along the ΓK-direction. From the DFT-derived Kohn-Sham states we deduce the EELS response without the inclusion of particle-hole attraction to study the possible role of the single-particle band structure on the exciton behavior. Based on this analysis we argue in favor of a strongly momentum dependent particle-hole interaction in WSe2 and other group VI-transition-metal dichalcogenides.
@article{arxiv.1604.01895,
title = {Non-Generic Dispersion of Excitons in the Bulk of WSe$_2$},
author = {R. Schuster and Y. Wan and M. Knupfer and B. Büchner},
journal= {arXiv preprint arXiv:1604.01895},
year = {2016}
}