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

Spins constitute a group of quantum objects forming key resource in modern technology. Two-dimensional (2D) van der Waals materials are fundamental interest for studying nanoscale magnetic phenomena. However, isolating singular paramagnetic spins 2D systems is challenging. We report here on emitting source embedded within hexgonal boron nitride (h-BN) exhibiting optical resonance (ODMR). extract an isotropic $g$ factor close to 2 and derive upper bound zero field splitting (ZFS) ($\leq$ 4 MHz). Photoluminescence (PL) behavior under temperature cycling using different excitations presented, assigning probable phonon lines (ZPLs) / side band (PSBs) emission peaks, compatible with h-BN's density states, indicating their intrinsic nature. Narrow inhomogeneous broadened ODMR differ significantly from monoatomic vacancy defect known literature. hyperfine coupling around 10 MHz. Its angular dependence indicates unpaired electron out-of-plane $\pi$-orbital, probably originating additional substitutional carbon impurity or other low mass atom. determine the spin relaxation time $T_1$ be 17 $\mu$s.