Influence of inter- and intra-valley carrier dynamics on the optical properties of monolayer TMDCs

First principle DFT-based microscopic many-body models are used to investigate inter- and intra-valley carrier dynamics in the monolayer transition-metal dichalcogenide MoTe2. Electron-electron and electron-phonon scatterings are calculated for transitions within the full Brillouin zone to determine overall carrier relaxation timescales as well as intra- and inter-valley transition rates. For excitation above the barriers separating bandstructure valleys carriers are found to relax on a ten femtosecond timescale into hot quasi-Fermi distributions at the band minima. Subsequently, the hot carrier plasma is cooled down on a picosecond timescale predominantly through emission of optical phonons. Local carrier occupations lead to strong energy renormalizations in momentum space. However, for the material investigated here, the global energy minimum remains at the K-points once carriers relax into global quasi-Fermi distributions. No transition from a direct to an indirect bandgap is observed. © 2022 SPIE.