Study of Doping-dependent Multiparticle Excitation Spectrum in Monolayer TMDCs from First Principles*

Monolayers of transition-metal dichalcogenides (TMDC), such as MoS₂, WSe₂, MoTe₂, have opened the door to the theoretical and experimental studies of multiparticle excitations, such as trions and biexcitons, with relatively large binding energies. Upon carrier doping or strong optical pump fluence, these excitation complexes dominate the optical properties of these materials owing to the strong Coulomb interactions and reduced electronic screening in such systems. In this work, we study, from first principles, how carrier doping affects the many-electron screening and renormalizes the exciton and trion linewidth in monolayer TMDCs. We employ interacting Green’s-function-based approaches, including the Bethe-Salpeter equation and beyond, to compute these multiparticle excitations. We show the valley- and momentum-resolved multiparticle excitations for various amounts of carrier dopings, and comment on the applicability of the traditional trion picture of one exciton plus an electron compared to the hybrid exciton plus Fermi-sea description to capture such excitations from first principles.