Single-spin resonance in a van der Waals embedded paramagnetic defect

A plethora of single-photon emitters have been identified in the atomic layers of two-dimensional van der Waals materials 1 – 8 . Here, we report on a set of isolated optical emitters embedded in hexagonal boron nitride that exhibit optically detected magnetic resonance. The defect spins show an isotropic g e -factor of ~2 and zero-field splitting below 10 MHz. The photokinetics of one type of defect is compatible with ground-state electron-spin paramagnetism. The narrow and inhomogeneously broadened magnetic resonance spectrum differs significantly from the known spectra of in-plane defects. We determined a hyperfine coupling of ~10 MHz. Its angular dependence indicates an unpaired, out-of-plane delocalized π -orbital electron, probably originating from substitutional impurity atoms. We extracted spin–lattice relaxation times T 1 of 13–17 μs with estimated spin coherence times T 2 of less than 1 μs. Our results provide further insight into the structure, composition and dynamics of single optically active spin defects in hexagonal boron nitride. The optically detected magnetic resonance of a single defect in hexagonal boron nitride is reported.