Monolayer-TMD excitons near phases of graphene multilayers

Graphene multilayers and transition metal dichalcogenides (TMDs) both have proven to be incredibly versatile in realizing and controlling exotic states of matter by engineering stacking arrangement, external fields, and proximity effects. In graphene, this includes correlated phases such as spin--valley magnetism, superconductivity, and most recently, the fractional quantum anomalous Hall effect in pentalayers. In monolayer TMDs, excitons with large binding energies dominate the optical response and are sensitive to the many-body states in nearby layers. In this theory work, we derive an explicit expression for the change in the effective electron-hole interaction in the TMD layers by accounting for screening induced by the charge polarizability of graphene multilayers. We use this interaction to explore the shifts in exciton binding energy and the TMD bandgap. We find that the TMD bandgap is significantly affected by screening, sensitive to properties around the Fermi energy of the multilayer graphene, the presence of cyclotron gaps ,and the interlayer distance between the TMD and multilayer graphene. Our theory paves the way to understanding how excitons in monolayer TMDs may act as probe to electronic phases in proximate materials.