Isotopic control of the boron-vacancy spin defect in hexagonal boron nitride

TL;DR

This study investigates how isotopic engineering of hexagonal boron nitride influences boron-vacancy spin defects, revealing improved ESR properties and enabling nuclear polarization, thus advancing quantum sensing applications.

Contribution

It demonstrates that isotopic purification of hBN enhances the ESR spectral resolution and enables nuclear polarization, providing a new platform for quantum technologies.

Findings

Isotopic purification simplifies hyperfine structure.

Purification with $^{10}$B yields narrower ESR linewidths.

Optical polarization of $^{15}$N nuclei achieved in isotopically-engineered hBN.

Abstract

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