Photophysical Characteristics of Boron Vacancy-Derived Defect Centers in Hexagonal Boron Nitride

Abstract

Single photon emitter (SPE) sources are important building blocks for photonics-based quantum technologies. Recently, the highly bright and versatile SPEs from the two-dimensional insulator material hexagonal boron nitride (hBN) have attracted significant research interest. However, due to the variability of emitter species and properties, an exact correlation between the underlying atomistic structures and their photo-physical properties is still lacking. In this work, we study six boron vacancy-derived defect centers in hBN ($V_B^-$, $V_B$+$H$, $V_{B2}$, $V_BC_N$, $V_BC_N^-$, and $V_BC_NC_N$) using advanced first principles techniques, characterizing their quasiparticle defect levels, optical spectra and excitation energies, and magneto-resonance properties. These defects have been chosen because of their relatively low formation energies, and, importantly, because they are amenable to intentional creation under experimental conditions. We establish the correlation between the underlying defect atomic structure and their photo-physical properties, thus facilitating the identification of SPEs that have already been observed in experiments. Our results lead to clear insights into very recent experiments where hBN SPEs can be controlled intentionally. On the other hand, our results also serve as guidelines for the bottom-up design of defect emitter centers in hBN for target applications that require specific defect properties, such as emission in the telecom wavelength, optical addressability and high radiative decay rates. This work thus provides a comprehensive understanding of the photo-physical characteristics of $V_B$-derived defect emitting centers, aiding in their identification and manipulation for tailored applications.