Role of dephasing in the absorption energies of excitons coupled to coherent phonons: A case study of MoS2

In this work, we perform ab initio real-time simulations using a relatively simple many-body method that provides an accurate description of the interaction between excitons and coherent phonons. Electronic correlations are treated at the GW level with ground-state static screening, while electron-nuclear interactions are handled using the Ehrenfest approximation. The calculated transient absorption spectrum exhibits coherent oscillations in the position of the excitonic peaks. We show that the amplitude of these oscillations depends on the exciton-coherent-phonon coupling as well as on the dephasing time of the polarization. These results corroborate and extend the general theory of the interaction between excitons and coherent phonons, offering new insights in the understanding of ultrafast dynamics of two-dimensional materials.