Effect of Coulomb interactions on optical properties of monolayer transition-metal dichalcogenides

A theoretical investigation is carried out on the effect of Coulomb interactions on the optical properties of monolayer transition-metal dichalcogenides (TMDCs) by solving the Bethe-Salpeter equation under the $k\ifmmode\cdot\else\textperiodcentered\fi{}p$ approximation. The calculated absorption spectrum of TMDCs exhibits strong exciton features, and a peculiar optical selection rule is found for circularly polarized light, in agreement with previous theoretical calculations and experimental observations. The exciton-exciton annihilation rate is evaluated by considering the Auger recombination process, which gives rise to the nonlinear optical response. The calculation results agree well with the experimental data, and confirm strong exciton-exciton interaction effects in monolayer TMDCs.