Observation of interlayer excitons in MoSe2 single crystals

Interlayer excitons with direct optical transitions are observed coexisting with intralayer excitons in the same $K$ valleys in bilayer, few-layer, and bulk ${\mathrm{MoSe}}_2$ single crystals by confocal reflection contrast spectroscopy. Quantitative analysis using the Dirac-Bloch equations provides unambiguous state assignment of all the measured resonances. The interlayer excitons in bilayer ${\mathrm{MoSe}}_2$ have a large binding energy of 153 meV and a narrow linewidth of 20 meV. Their spectral weight is comparable to the commonly studied higher-order intralayer excitons. At the same time, the interlayer excitons are characterized by distinct transition energies and permanent dipole moments, providing a promising high temperature and optically accessible platform for dipolar exciton physics.