  Our examination of the interplay of ultrafast charge dynamics and
electron-phonon interaction in bilayer MoS2 provides a microscopic basis for
understanding the features (two peaks) in the emission spectrum. We demonstrate
that while the initial accumulation of excited charge occurs at and near the Q
point of the two-dimensional Brillioun zone, emission takes place predominantly
through two pathways: direct charge recombination at the K point and indirect
phonon-assisted recombination of electrons at the K valley and holes at
{\Gamma} hill of the Brillouin zone. Analysis of the wave vector dependencies
of the electron-phonon interaction traces the higher energy peak to
phonon-assisted relaxation of the excited electrons from the Q to the K valley
in the conduction band. Our results thus reveal the importance of ultrafast
charge dynamics in understanding photoemissive properties of a few-layer
transition-metal dichalcogenide. These calculations are based on time dependent
density functional theory in the density matrix formulation.
