Magneto-optical spectra of the split nickel-vacancy defect in diamond

Nickel is a common impurity in high-pressure high-temperature diamond and may contaminate chemical vapor deposited used for high-power electronics or quantum technology applications. Magneto-optical fingerprints of nickel have been known since decades, however, no consensus has reached about the microscopic origins nickel-related electron paramagnetic resonance, photoluminescence, optically detected magnetic resonance spectra. The unknown defect structures make it difficult to control them harness given application. As consequence, considered as an that should be avoided its concentration minimized. Recent advances development ab initio magneto-optical spectroscopy significantly increased accuracy predictive power can employed identification in-depth characterization color centers diamond. In this study, we extend tools towards self-consistent calculation second-order spin-orbit coupling solids. We apply full arsenal characterize split nickel-vacancy which one most stable configurations. result, optical are positively identified various charge states particular, 1.40-eV center NIRIM-2 single negative state center. possesses $S=\frac{1}{2}$ spin with orbital doublet ground state. find coherence time ground-state 0.1 ms at cryogenic temperatures initialized readout by $\mathrm{\ensuremath{\Lambda}}$-scheme protocol. Since inversion symmetry signal insensitive stray electric fields, advantage creating indistinguishable solid-state single-photon sources. predict negatively charged similar properties those well-known silicon-vacancy but superior terms times. Our study resolves few decades controversy turns from resource