Observation of Wannier-Rydberg and Charge-Transfer Hybrid Moiré Excitons under Pressure

Abstract

Moiré superlattices in van der Waals heterostructures, arising from lattice mismatch or twist angle, provide a powerful platform for engineering correlated electronic and excitonic states. Moiré excitons form when electrons and holes are individually modulated by the moiré potential yet remain bound by Coulomb interaction, resulting in exciton wave functions with a highly nontrivial and rich real-space structure. However, achieving and dynamic control over the interplay between excitonic Coulomb interaction and the moiré potential remains a central challenge. Here, we demonstrate that hydrostatic pressure provides a continuous and effective means of enhancing the moiré potential and tuning moiré excitons in WSe 2 / WS 2 moiré heterobilayers. As pressure increases, intralayer moiré excitons exhibit systematic redshifts as the moiré potential deepens. Crucially, above ∼ 3     GPa the system enters a strong-moiré regime, where a new higher-energy intralayer moiré exciton emerges that is not accessible otherwise. Combining dual-gate optical spectroscopy with Bethe-Salpeter equation calculations, we reveal that this emerging moiré exciton state arises from strong pressure-induced hybridization between two distinct exciton series: Wannier-Rydberg and charge-transfer excitons. Enhanced exciton-electron and exciton-exciton interactions observed in doping-dependent photoluminescence further evidence the strengthened moiré potential under pressure. Our work establishes a pioneering paradigm of moiré excitonic wave function engineering, enabling the on-demand creation of tailored excitonic species in moiré superlattices.