Resonant Photo-Luminescence Excitation Spectroscopy Experiments and Homogenous vs. Inhomogenous Broadening in MoSe₂ Monolayers

Data from resonant photoluminescence excitation spectroscopy experiments performed on the monolayer transition metal dichalcogenide (TMDC) MoSe₂ are presented. The excitation laser is scanned across the exciton and trion optical frequencies, and at each excitation wavelength a spectrum of the emitted light is measured. This data gives unique insight into the homogenous and inhomogenous broadening present in monolayer TMDC materials. In monolayer MoSe₂ samples exfoliated on to glass or SiO₂ on silicon, we measure homogenous linewidths of ~2 meV. The homogenous linewidth is much more uniform than the inhomogenous linewidth, both between and within flakes. Encapsulation in hexagonal boron nitride somewhat reduces the homogenous linewidth, possibly by some combination of altering the coupling of the exciton to phonon modes and altering the radiative coupling to the environment. We also investigate the degree of linear polarization of the emitted light as a function of both excitation and emission wavelength. This gives insight into the decoherence between the superposition of excitons created at both the K and K^' points under excitation with linearly polarized light.