Exciton-phonon relaxation bottleneck and radiative decay of thermal   exciton reservoir in two-dimensional materials
  We study exciton radiative decay in a two-dimensional material, taking into account large thermal population in the non-radiative states, from which excitons are scattered into the radiative states by acoustic phonons. We find an analytical solution of the kinetic equation for the non-equilibrium distribution function of excitons in the radiative states. Our estimates for bright excitons in transition metal dichalcogenides indicate a strong depletion of radiative state population due to insufficient exciton-phonon scattering rate at low temperatures. 
A. O. Slobodeniuk, D. M. Basko
cond-mat.mes-hall