Observation of exciton-phonon coupling in MoSe 2 monolayers

The interaction of excitons with phonons governs energy relaxation, dephasing, and optical transition line broadening with temperature in two-dimensional (2D) materials. Here, the authors observe and study unusual high-energy tails in both absorption and emission extending over several meV in energy at low temperatures. They develop a theory of the effect and show that the coupling between acoustic phonons and excitons lies at the origin for the observed high-energy tails. This work demonstrates that the exciton-phonon coupling in 2D crystals is more efficient as compared with conventional semiconductor structures, such as GaAs/AlGaAs quantum wells.