Phonon‐Dressed States of Dark Excitons in Transition Metal Dichalcogenides

ABSTRACT Electron–phonon interactions strongly influence exciton dynamics, enabling control at the nanoscale over light‐matter interactions and coherent phenomena for emerging quantum sensing applications. In transition metal dichalcogenides, momentum‐forbidden dark excitons occupy the energy ground state and exhibit exceptional sensitivity to their local environment. Here, we optically characterize these dark excitonic states in WS 2 and WSe 2 monolayers by tuning their band alignment through strain. We unveil their pronounced localization, extended lifetimes, and high linear polarization, signatures of strong exciton–phonon coupling and environmental responsiveness. Multiple distinct emission peaks are consistent with phonon‐dressed excitonic replicas with an estimated Huang‐Rhys factor of about 5. Density functional theory calculations, combined with measured strain‐dependent emission energies, constrain the relevant energy scales and suggest possible phonon‐assisted pathways underlying these phonon‐dressed states. Because replica energies, relative spectral weights, polarization axis, and lifetime respond to environmental factors such as local strain, dielectric environment, and phonon populations, these phonon‐dressed dark excitons provide a materials platform for exciton‐based nanoscale sensing and coherent control in 2D semiconductors.