Bosonic Delocalization of Dipolar Moir\'e Excitons

Abstract

In superlattices of twisted semiconductor monolayers, tunable moir\'e potentials emerge, trapping excitons into periodic arrays. In particular, spatially separated interlayer excitons are subject to a deep potential landscape and they exhibit a permanent dipole providing a unique opportunity to study interacting bosonic lattices. Recent experiments have demonstrated density-dependent transport properties of moir\'e excitons, which could play a key role for technological applications. However, the intriguing interplay between exciton-exciton interactions and moir\'e trapping has not been well understood yet. In this work, we develop a microscopic theory of interacting excitons in external potentials allowing us to tackle this highly challenging problem. We find that interactions between moir\'e excitons lead to a delocalization at intermediate densities and we show how this transition can be tuned via twist angle and temperature. The delocalization is accompanied by a modification of optical moir\'e resonances, which gradually merge into a single free exciton peak. The predicted density-tunability of the supercell hopping can be utilized to control the energy transport in moir\'e materials.