DC Magnetic Field Sensitivity Optimization of Spin Defects in Hexagonal Boron Nitride.

Spin defects existing in van der Waals materials attract wide attention thanks to their natural advantages for quantum sensing, especially the negatively charged boron vacancy (V) centers in hexagonal boron nitride (-BN). Here we systematically investigate the laser and microwave power broadening in continuous-wave optically detected magnetic resonance (ODMR) of the V ensemble in -BN, by revealing the behaviors of ODMR contrast and line width as a function of the laser and microwave powers. The experimental results are well explained by employing a two-level simplified model of ODMR dynamics. Furthermore, with optimized power, the DC magnetic field sensitivity of V ensemble is significantly improved up to 2.87 ± ± 0.07 μT/. Our results provide important suggestions for further applications of V centers in quantum information processing and ODMR-based quantum sensing.