Ensemble nuclear polarization in diamond in a broad range of magnetic fields*

Nuclear polarization via optical pumping of the nitrogen-vacancy (NV) centers in diamond has drawn recent attention due to its importance for understanding the fundamental processes involving the centers in applications such as optical hyperpolarization of nuclei. We have studied polarization of the ¹⁴N nuclei constituent to NV centers in a broad range of magnetic fields, from zero to above the magnetic field of ≈ 0.1 T corresponding to the ground-state level anticrossing (GSLAC). We observe sharp drops in the polarization superimposed on top of a broader regular dependence including resonance peaks at 51.2 mT and 102.4 mT, reported in [1] and [2]. The widths of the sharp features are approximately 0.33 mT full width at half maximum at 59 mT and 0.78 mT close to GSLAC. A theoretical explanation describing all these features will be provided.

[1] V. Jacques, P. Neumann, et al., Phys. Rev. Lett. 102, 057403 (2009).
[2] V. Ivády, K. Szász, et al., Physical Review B 92, 115206 (2015).