Isotope Engineering for Spin Defects in hexagonal boron nitride

Spin defects in layered van der Waals materials, such as hexagonal boron nitride (hBN), are increasingly gaining attention for their potential in quantum technological applications. In this study, we employ isotope engineering to notably enhance the coherence properties of these embedded spin defects. By employing isotopically enriched h10B15N crystals, we have realized clear enhancements in spin transitions related to the negatively charged boron vacancy centers (VB-). In direct comparison with naturally isotopic hBN, our material shows transitions that are both narrower and less overlapped. This leads to an improvement in both coherence time T2 and relaxation time T1. As a result, the VB- defects in our engineered samples exhibit enhancements of up to 4 times in DC and twice in AC magnetic field sensitivities. Our results highlight the utility of VB- defects in our isotopically pure hBN over the conventional naturally abundant ones for sensing applications, and also point to the potential of this material in creating multi-qubit quantum registers, thanks to the individual addressability of its electronic and nuclear spins. The methodology of isotope engineering adopted in this study is not limited to hBN but more broadly in the van der Waals materials family.