Revealing localized excitons in WSe₂/β-Ga₂O₃

We have investigated the optical and magneto-optical properties of monolayer (ML) WSe₂ on flakes of β-Ga₂O₃ under high magnetic fields. Remarkably, sharp emission peaks were observed and associated with localized excitons related to point defects. A detailed study of low-temperature photoluminescence (PL) and magneto-PL under high perpendicular magnetic field up to 9 T was carried out. Several sharp emission peaks have shown valley g-factors values close to −4, which is an unusual result for localized excitons in WSe₂. Furthermore, some PL peaks have shown higher g-factor values of ≈ −7 and ≈ −12, which were associated with the hybridization of strain localized dark excitons and defects. The reported results suggest that β-Ga₂O₃ is, indeed, a promising dielectric substrate for ML WSe₂ and also to explore fundamental physics in view of possible applications in quantum information technology.