Exploration of the bright and dark exciton landscape and fine structure of MoS2 using G0W0-BSE

Spectral ordering between dark and bright excitons in transition-metal dichalcogenides is of increasing interest for optoelectronic applications. However, little is known about dark exciton energies and their binding energies. We report the exciton landscape including momentum-forbidden dark excitons of the MoS2 monolayer using single-shot GW–Bethe Salpeter equation (G0W0-BSE) calculations. We find the lowest-energy exciton to be indirect at (Kv′→Kc), in agreement with recent GdW-BSE calculations [T. Deilmann and K. S. Thygesen, 2D Mater. 6, 035003 (2019)10.1088/2053-1583/ab0e1d]. We also find that by and large, the lowest-energy dark exciton binding energies (Eb) scale with the quasiparticle energies (Eg) according to the empirical Eb/Eg=0.25 rule. Differences in exciton binding energies are explained using an orbital theory.