Analytical description of the 1s exciton linewidth temperature dependence in transition metal dichalcogenides

We obtain an analytical expression for the linewidth of the 1s exciton as a function of temperature in transition metal dichalcogenides. The total linewidth, as a function of temperature, is dominated by three contributions: (i) the radiative decay (essentially temperature independent), (ii) the phonon-induced intravalley scattering, and (iii) the phonon-induced intervalley scattering. Our approach uses a variational Ansatz to solve the Wannier equation, allowing for an analytical treatment of the excitonic problem, including rates of the decay dynamics. Our results are in good agreement with experimental data already present in the literature and can be used to readily predict the value of the total linewidth at any temperature in the broad class of excitonic two-dimensional materials.