Theory of exciton-phonon coupling

The effects of the electron-phonon interaction on optical excitations can be understood in terms exciton-phonon coupling, and require a careful treatment low-dimensional materials with strongly bound excitons or strong electron-hole general. Through phonon absorption emission processes, optically accessible are scattered into otherwise dark finite-momentum exciton states. We derive practical expression for phonon-induced term self-energy (denoted as self-energy) that gives temperature dependence transition energies their lifetime broadening resulting from exciton's phonons. illustrate this theory two-dimensional model, show our differs qualitatively previous expressions found literature neglect binding correlations.