Magnetic brightening and its dynamics of defect-localized exciton emission in monolayer two-dimensional semiconductor.

Quantum light sources, especially single-photon emitters, are crucial for advancing quantum technologies. Despite extensive research, the behavior of defect-localized excitons in monolayer WSe under external perturbations, such as magnetic fields, remain underexplored. This study investigates the nature and dynamics of defect-localized excitons under in-plane magnetic fields using steady-state and time-resolved photoluminescence (PL) spectroscopy. Observations reveal a sharp PL peak, indicative of single-photon emission, with doublet peaks from hybridized spin-state excitons. Notably, magnetic brightening of the PL peak was detected at a low magnetic field (<1 tesla), and the dynamics of hybridized-state excitons under magnetic fields indicated field-induced state mixing, explaining the magnetic brightening. These findings advance tunable single-photon emitters controlled by magnetic fields, with implications for quantum optics applications.