Theory of interlayer exciton dynamics in two-dimensional transition metal dichalcogenide heterolayers under the influence of strain reconstruction and disorder

Monolayers of transition metal dichalcogenides (TMDC) became one of the most studied nanostructures in the last decade. Combining two different TMDC monolayers results in a heterostructure whose properties can be individually tuned by the twist angle between the lattices of the two van der Waals layers and the relative placement of the layers, leading to moir\'e cells. For small twist angles, lattice reconstruction leads to strong strain fields in the moir\'e cells. In this paper, we combine an existing theory for lattice reconstruction with a quantum dynamic theory for interlayer excitons and their dynamics due to exciton-phonon scattering using a polaron transformation. The exciton theory is formulated in real space instead of the commonly used quasimomentum space to account for imperfections in the heterolayer breaking lattice translational symmetry. We can analyze the structure of the localized and delocalized exciton states and their exciton-phonon scattering rates for single phonon processes using Born-Markov approximation and multiphonon processes using a polaron transformation. Furthermore, linear optical spectra and exciton relaxation Green's functions are calculated and discussed. A P-stacked MoSe₂/WSe₂ heterolayer is used as an illustrative example. It shows excitons localized in the potential generated through the moir\'e-pattern and strain and a delocalized continuum. The exciton-phonon relaxation times vary depending on the strain and range from subpicoseconds up to nanoseconds.