Probing the Optical Dynamics of Quantum Emitters in Hexagonal Boron Nitride*

Hexagonal boron nitride (h-BN) is a van der Waals material that hosts defect-based quantum emitters (QEs) at room temperature. Recent observations suggest existence of multiple distinct defect structures hosting QEs. Theoretical proposals suggest vacancies, their complexes and substitutional atoms as likely defect candidates. However, experimental identification of the QEs’ electronic structure is lacking, and key details of the QEs’ charge and spin properties remain unknown. Here, we probe the optical dynamics of QEs in h-BN using photon emission (PE) statistics and photoluminescence (PL) spectroscopy for various excitation powers and wavelengths. The PL spectra exhibit emission lineshapes consistent with individual phonon-assisted optical transitions. However, the PE statistics reveal complicated optical dynamics and suggest there are multiple non-radiative transitions consistent with electronic and charge states. Remarkably, the QEs’ antibunching and bunching rates scale nonlinearly with the optical pumping rate, suggesting the existence of short-lived states and multiple charge or spin manifolds as key elements in the QEs’ optical dynamics. We compare these observations to theoretical models of the QEs’ electronic structure.