Dynamically tunable moiré exciton Rydberg states in a monolayer semiconductor on twisted bilayer graphene

Moire excitons are emergent optical excitations in two-dimensional semiconductors with moire superlattice potentials. Although these excitations have been observed on several platforms, a system with dynamically tunable moire potential to tailor their properties is yet to be realized. Here we present a continuously tunable moire potential in monolayer WSe2, enabled by its proximity to twisted bilayer graphene (TBG) near the magic angle. By tuning local charge density via gating, TBG provides a spatially varying and dynamically tunable dielectric superlattice for modulation of monolayer WSe2 exciton wave functions. We observed emergent moire exciton Rydberg branches with increased energy splitting following doping of TBG due to exciton wave function hybridization between bright and dark Rydberg states. In addition, emergent Rydberg states can probe strongly correlated states in TBG at the magic angle. Our study provides a new platform for engineering moire excitons and optical accessibility to electronic states with small correlation gaps in TBG. The authors demonstrate the tunability of moire potential and emergent moire exciton Rydberg states in a monolayer transition metal dichalcogenide governed by an adjacent twisted bilayer graphene near the magic angle with gate-tunable local charge density.