Effective long-range attraction of moir\'e excitons under the influence of atomic reconstructions and anisotropic screening

Abstract

The moir\'e pattern, which emerges due to a relative rotation between two monolayers of transition metal dichalcogenides, features a long lattice period for small twist angles. The resulting band structure modulation acts as an effective potential for interlayer excitons (IXs), which can realize correlated many-body phenomena. Here, we aim for a material-realistic modelling of the exciton-exciton interaction, taking into account lattice reconstructions and an exciton-exciton potential that incorporates the highly anisotropic screening imposed by the two-dimensional bilayer and the dielectric background. We find strong modifications of the on-site interaction induced by the change of the moir\'e potential during lattice reconstructions, while for long-range interactions on the length scale of the moir\'e period, anisotropic dielectric screening leads to a crossover from a repulsive to an attractive interaction. The interaction potential and hopping amplitudes serve as parameters for a Bose-Hubbard model on the moir\'e lattice, which we use to explain correlated behavior of interlayer excitons.