Multiphonon replicas of the excitonic spectroscopy in monolayer transition metal chalcogenides

Within the framework of the Huang–Rhys model, we study multiphonon replicas of excitonic spectroscopy in monolayer transition metal chalcogenides based on excitons coupled with three types of phonon modes. The phonon replicas for the longitudinal optical (LO) phonon modes and surface optical (SO) phonon modes induced by the polar substrate Al 2O 3 are given and a linewidth of the phonon replica arising from the exciton-longitudinal acoustic phonon interaction is proposed. We find that the intensity distribution and temperature dependence of the phonon replicas are in good agreement with the experimental measurement. Furthermore, we propose combinational phonon replicas of p L O ℏ ω L O + p S O ℏ ω S O between two optical phonon modes, which effectively fill the gaps between the replicas of the single phonon modes. These theoretical results provide some insight into the detailed analysis of excitonic spectroscopy.