Excitons dominate the optical properties of monolayer transition metal dichalcogenides (TMDs). Besides optically accessible bright exciton states, TMDs exhibit also a multitude of optically forbidden dark excitons. Here, we show that efficient exciton-phonon scattering couples bright and dark states and gives rise to an asymmetric excitonic line shape. The observed asymmetry can be traced back to phonon-induced sidebands that are accompanied by a polaron redshift. We present a joint theory-experiment study investigating the microscopic origin of these sidebands in different TMD materials taking into account intra- and intervalley scattering channels opened by optical and acoustic phonons. The gained insights contribute to a better understanding of the optical fingerprint of these technologically promising nanomaterials.
@article{arxiv.1711.08691,
title = {Phonon Sidebands in Transition Metal Dichalcogenides},
author = {Dominik Christiansen and Malte Selig and Gunnar Berghäuser and Robert Schmidt and Iris Niehues and Robert Schneider and Ashish Arora and Steffen Michaelis de Vasconcellos and Rudolf Bratschitsch and Ermin Malic and Andreas Knorr},
journal= {arXiv preprint arXiv:1711.08691},
year = {2017}
}