A fully microscopic model of the doping-dependent exciton and trion linewidths in the absorption spectra of monolayer transition metal dichalcogenides in the low temperature and low-doping regime is explored. The approach is based on perturbation theory and avoids the use of phenomenological parameters. In the low-doping regime, we find that the trion linewidth is relatively insensitive to doping levels, while the exciton linewidth increases monotonically with doping. On the other hand, we argue that the trion linewidth shows a somewhat stronger temperature dependence. The magnitudes of the linewidths are likely to be masked by phonon scattering for T ≥ 20 K in encapsulated samples in the low-doping regime. We discuss the breakdown of perturbation theory, which should occur at relatively low-doping levels and low temperatures. Our work also paves the way toward understanding a variety of related scattering processes, including impact ionization and Auger scattering in clean 2D samples.
REFERENCES
Recent unpublished experimental results by K. Wagner, E. Wietek, and J. Zipfel in the group of Alexey Chernikov have given access to linewidths as a function of doping in the low-doping regime in clean, encapsulated WSe2 at 5 K. While the data fill in the upper end of the doping regime we present in our Fig. 1, they are in reasonable agreement with our results, including monotonically increasing (with doping level n) exciton lines of width 5–10 meV, a somewhat larger growth for the 2s line as compared to 1s, and a nearly flat trion line that initially slightly decreases with increasing n. We thank Alexey Chernikov for sharing these results to us after the submission of this work.