Exciton Dynamics in Monolayer WSe₂

Two-dimensional semiconductors exhibit strongly bound excitons with unconventional dynamics. Here we investigate ultrafast exciton dynamics in monolayer WSe₂ from first principles, using our newly developed formalism to compute exciton-phonon interactions [1] and nonequilibrium exciton dynamics. We present accurate predictions of the temperature-dependent bright exciton photoluminescence (PL) linewidth and the phonon-assisted PL spectrum, including details of the vibronic structure. We further analyze the dominant exciton scattering channels in WSe₂, generating maps of phonon momentum-and mode-dependent exciton relaxation processes. We solve the time-dependent exciton Boltzmann transport equation (BTE) to explicitly simulate nonequilibrium exciton dynamics, and present simulated time-resolved ARPES results to connect our findings with experiments. Real-time tracking of the exciton occupations also reveals details of the bright exciton dephasing on femtosecond time scale. Our work advances the understanding of exciton scattering processes and excited-state dynamics in WSe₂.

[1] H.-Y. Chen, D. Sangalli, and M. Bernardi. Phys. Rev. Lett., 125 107401