Key properties of nine possible defect sites in hexagonal boron nitride (h-BN), $V_{\mathrm{N}},{V_{\mathrm{N}}}^{-1},{\mathrm{C}}_{\mathrm{N}},V_{\mathrm{N}}{\mathrm{O}}_{2\mathrm{B}},V_{\mathrm{N}}{\mathrm{N}}_{\mathrm{B}},V_{\mathrm{N}}{\mathrm{C}}_{\mathrm{B}},V_{\mathrm{B}}{C}_{\mathrm{N}},V_{\mathrm{B}}{\mathrm{C}}_{\mathrm{N}}\mathrm{S}{\mathrm{i}}_{\mathrm{N}}$, and $V_{\mathrm{N}}{\mathrm{C}}_{\mathrm{B}}\mathrm{S}{\mathrm{i}}_{\mathrm{B}}$, are predicted using density-functional theory and are corrected by applying results from high-level ab initio calculations. Observed h-BN electron-paramagnetic resonance signals at 22.4, 20.83, and 352.70 MHz are assigned to $V_{\mathrm{N}},{\mathrm{C}}_{\mathrm{N}}$, and $V_{\mathrm{N}}{\mathrm{O}}_{2\mathrm{B}}$, respectively, while the observed photoemission at 1.95 eV is assigned to $V_{\mathrm{N}}{\mathrm{C}}_{\mathrm{B}}$. Detailed consideration of the available excited states, allowed spin-orbit couplings, zero-field splitting, and optical transitions is made for the two related defects $V_{\mathrm{N}}{\mathrm{C}}_{\mathrm{B}}$ and $V_{\mathrm{B}}{C}_{\mathrm{N}}$. $V_{\mathrm{N}}{\mathrm{C}}_{\mathrm{B}}$ is proposed for realizing long-lived quantum memory in h-BN. $V_{\mathrm{B}}{C}_{\mathrm{N}}$ is predicted to have a triplet ground state, implying that spin initialization by optical means is feasible and suitable optical excitations are identified, making this defect of interest for possible quantum-qubit operations.

• Received 24 October 2017
• Revised 21 December 2017

DOI:https://doi.org/10.1103/PhysRevB.97.064101