  Enhanced Coulomb interactions in monolayer transition metal dichalcogenides
cause tightly bound electron-hole pairs (excitons) which dominate their linear
and nonlinear optical response. The latter includes bleaching, energy
renormalizations, and higher-order Coulomb correlation effects like biexcitons
and excitation-induced dephasing (EID). While the first three are extensively
studied, no theoretical footing for EID in exciton dominated semiconductors is
available so far. In this study, we present microscopic calculations based on
excitonic Heisenberg equations of motion and identify the coupling of optically
pumped excitons to exciton-exciton scattering continua as the leading mechanism
responsible for an optical power dependent linewidth broadening (EID) and
sideband formation. Performing time-, momentum-, and energy-resolved
simulations, we quantitatively evaluate the EID for the most common monolayer
transition metal dichalcogenides and find an excellent agreement with recent
experiments.
