Local and bulk 13C hyperpolarization in nitrogen-vacancy-centred diamonds at variable fields and orientations

Polarizing nuclear spins is of fundamental importance in biology, chemistry and physics. Methods for hyperpolarizing C-13 nuclei from free electrons in bulk usually demand operation at cryogenic temperatures. Room temperature approaches targeting diamonds with nitrogen-vacancy centres could alleviate this need; however, hitherto proposed strategies lack generality as they demand stringent conditions on the strength and/or alignment of the magnetic field. We report here an approach for achieving efficient electron-C-13 spin-alignment transfers, compatible with a broad range of magnetic field strengths and field orientations with respect to the diamond crystal. This versatility results from combining coherent microwave-and incoherent laser-induced transitions between selected energy states of the coupled electron-nuclear spin manifold. C-13-detected nuclear magnetic resonance experiments demonstrate that this hyperpolarization can be transferred via first-shell or via distant Cs-13 throughout the nuclear bulk ensemble. This method opens new perspectives for applications of diamond nitrogen-vacancy centres in nuclear magnetic resonance, and in quantum information processing.