Interplay between structural and excited-state properties of twisted TMDC moiré heterostructures

The synthesis of quasi-two-dimensional materials, such as monolayer transition metal dichalcogenides (TMDCs), opened the door to studying new classes of systems with nanoscale dimensionality confinement and weak electronic screening, leading to strongly enhanced electron interactions. More recently, there has been a growing interest in studying the electronic and optical properties in heterobilayers of such materials, which support moiré structures and interlayer excitons. However, the interplay between the structural and excited-state properties of such materials is poorly understood, often relying on empirically fitted continuum models. In this talk, we present results obtained from recent formalisms and methods we developed to bridge these two phenomena. First, derive the time-resolved angle-resolved photoemission spectroscopy (TR-ARPES) signature of moiré excitons. Our calculations are in good agreement with recent experiments, and show that moiré excitons can be localized to a surprising extent in the moiré cell, being well-localized even for relatively large twist angles (~2°) – associated with a moiré lattice parameter of ~ 6 nm. We also comment on a new method to extract accurate moiré potentials from first principles, and show why previous ab initio approaches often yield potential depths that are significantly smaller than those deduced from experiment. We also show how such realistically deduced potentials lead to moiré-modulated interlayer excitons with qualitatively different characters.