Two-electron-spin ratchets as a platform for microwave-free dynamic nuclear polarization of arbitrary material targets

Optically pumped color centers in semiconductor powders can potentially induce high levels of nuclear spin polarization in surrounding solids or fluids at or near ambient conditions, but complications stemming from the random orientation of the particles and the presence of unpolarized paramagnetic defects hinder the flow of polarization beyond the defect's host material. Here, we theoretically study the spin dynamics of interacting nitrogen-vacancy (NV) and substitutional nitrogen (P1) centers in diamond to show that outside protons spin-polarize efficiently upon a magnetic field sweep across the NV-P1 level anticrossing. The process can be interpreted in terms of an NV-P1 spin ratchet, whose handedness, and hence the sign of the resulting nuclear polarization, depends on the relative timing of the optical excitation pulse. Further, we find that the polarization transfer mechanism is robust to NV misalignment relative to the external magnetic field, and efficient over a broad range of electron-electron and electron-nuclear spin couplings, even if proxy spins feature short coherence or spin-lattice relaxation times. Therefore, these results pave the route toward the dynamic nuclear polarization of arbitrary spin targets brought in proximity with a diamond powder under ambient conditions. Fil: Zangara, Pablo René. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. City University of New York. The City College of New York; Estados Unidos Fil: Henshaw, Jacob. City University of New York. The City College of New York; Estados Unidos Fil: Pagliero, Daniela. City University of New York. The City College of New York; Estados Unidos Fil: Ajoy, Ashok. Lawrence Berkeley National Laboratory; Estados Unidos. University of California at Berkeley; Estados Unidos Fil: Reimer, Jeffrey A.. Lawrence Berkeley National Laboratory; Estados Unidos. University of California at Berkeley; Estados Unidos Fil: Pines, Alexander. University of California at Berkeley; Estados Unidos. Lawrence Berkeley National Laboratory; Estados Unidos Fil: Meriles, Carlos A.. City University of New York. The City College of New York; Estados Unidos. University of California at Berkeley; Estados Unidos