Origin of nonclassical light emission from defects in multi-layer hexagonal boron nitride

Abstract: In recent years, mono-layers and multi-layers of hexagonal boron nitride (hBN) have been demonstrated as host materials for localized atomic defects that can be used as emitters for ultra-bright, non-classical light. The origin of the emission, however, is still subject to debate. Based on measurements of photon statistics, lifetime and polarization on selected emitters we find that these atomic defects do not act as pure single photon emitters. Our results strongly and consistently indicate that each zero phonon line of individual emitters is comprised of two independent electronic transitions. These results give new insights into the nature of the observed emission and hint at a double defect nature of emitters in multi-layer hBN.