Isotopic Control of the Boron-Vacancy Spin Defect in Hexagonal Boron Nitride

We report on electron spin resonance (ESR) spectroscopy of boron-vacancy (V-B(-)) centers hosted in isotopically engineered hexagonal boron nitride (hBN) crystals. We first show that isotopic purification of hBN with N-15 yields a simplified and well-resolved hyperfine structure of V-B(-) centers, while purification with B-10 leads to narrower ESR linewidths. These results establish isotopically purified h(10)B(15)N crystals as the optimal host material for future use of V-B(-) spin defects in quantum technologies. Capitalizing on these findings, we then demonstrate optically induced polarization of N-15 nuclei in h(10)B(15)N, whose mechanism relies on electron-nuclear spin mixing in the V-B(-) ground state. This work opens up new prospects for future developments of spin-based quantum sensors and simulators on a two-dimensional material platform.