Photophysics of quantum emitters in hexagonal boron-nitride nano-flakes
Mads Boll, Ilya P. Radko, Alexander Huck, Ulrik L. Andersen
Abstract
Quantum emitters in hexagonal boron nitride (hBN) have attracted significant interest due to their bright and narrowband photon emission even at room temperature. The wide-bandgap two-dimensional material incorporates crystal defects of yet-unknown configuration, introducing discrete energy levels with radiative transition frequencies in the visible spectral range. The commonly observed high brightness together with the moderate fluorescence lifetime indicates a high quantum efficiency, but the exact dynamics and the underlying energy level structure remain elusive. In this study we present a systematic and detailed analysis of the photon statistics recorded for several individual emitters. We extract the individual decay rates by modeling the second-order correlation functions using a set of rate equations based on an energy level scheme involving long-lived states. Our analysis clearly indicates excitation-power-dependent non-radiative couplings to at least two metastable levels and confirms a near unity quantum efficiency.