Nonlinear spectroscopy of excitonic states in transition metal dichalcogenides

Second-harmonic generation (SHG) is a well-known nonlinear spectroscopy method to probe electronic structure, specifically, in transition metal dichalcogenide (TMDC) monolayers. This work investigates the dynamics of strongly excited TMDC monolayer by solving time evolution equations for density matrix. It shown that presence excitons qualitatively changes leading, particular, huge enhancement signal as function dielectric environment. also SHG polarization angular diagram and its dependence on driving strength are very sensitive type exciton state. sensitivity suggests convenient tool analyzing fine structure excitonic states.