Fingerprinting Defects in Hexagonal Boron Nitride via Multi-Phonon Excitation

Single photon emitters in hexagonal boron nitride (hBN) have gathered a lot of attention due to their favorable emission properties and the manifold of possible applications. Despite extensive scientific effort, the exact atomic origin of these emitters has remained unknown thus far. Recently, several studies have tied the emission in the yellow spectral region to carbon-related defects, but the exact atomic structure of the defects remains elusive. In this study, photoluminescence emission and excitation spectroscopy is performed on a large number of emitters within this region. By comparing the experimental data with theoretical predictions, the origin of yellow single photon emission in hexagonal boron nitride is determined. Knowledge of this atomic structure and its optical properties is crucial for the reliable implementation of these emitters in quantum technologies.