Investigation of indirect excitons in bulk 2H-MoS2 using transmission electron energy-loss spectroscopy.

We have investigated indirect excitons in bulk 2H-MoS2 using transmission electron energy-loss spectroscopy. The electron energy-loss spectra were measured for various momentum transfer values parallel to the [Formula: see text] and [Formula: see text] directions of the Brillouin zone. The results allowed the identification of the indirect excitons between the valence band K v and conduction band Λc points, the Γv and K c points as well as adjacent K v and [Formula: see text] points. The energy-momentum dispersions for the K v-Λc, Γv-K c and K v1-[Formula: see text] excitons along the [Formula: see text] line are presented. The former two transitions exhibit a quadratic dispersion which allowed calculating their effective exciton masses based on the effective mass approximation. The K v1-[Formula: see text] transition follows a more linear dispersion relationship.