Magnetic field sensitivity and decoherence spectroscopy of an ensemble   of narrow-linewidth nitrogen-vacancy centers close to a diamond surface
  We perform pulsed optically detected electron spin resonance to measure the DC magnetic field sensitivity and electronic spin coherence time T_2 of an ensemble of near-surface, high-density nitrogen-vacancy (NV) centers engineered to have a narrow magnetic resonance linewidth. Combining pulsed spectroscopy with dynamic nuclear polarization, we obtain the photon-shot-noise-limited DC magnetic sensitivity of 35 nT Hz^{-0.5}. We find that T_2 is controlled by instantaneous diffusion, enabling decoherence spectroscopy on residual nitrogen impurity spins in the diamond lattice and a quantitative determination of their density. The demonstrated high DC magnetic sensitivity and decoherence spectroscopy are expected to broaden the application range for two-dimensional magnetic imaging. 
Kento Sasaki, Ed E. Kleinsasser, Zhouyang Zhu, Wen-Di Li, Hideyuki   Watanabe, Kai-Mei C. Fu, Kohei M. Itoh, Eisuke Abe
cond-mat.mes-hall