Two-Electron-Spin Ratchets as a Platform for Microwave-Free Dynamic Nuclear Polarization of Arbitrary Material Targets.

Pablo R Zangara,Carlos A Meriles,Jeffrey A Reimer,Alexander Pines,Jacob Henshaw,Daniela Pagliero,Ashok Ajoy

doi:10.1021/acs.nanolett.8b05114

Pablo R Zangara, Carlos A Meriles + Show 5 more

Open Access

https://doi.org/10.1021/acs.nanolett.8b05114

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Abstract

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.

Highlights

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication
We demonstrated that 13C spins in NV-hosting diamond particles can be efficiently polarized through the combined use of continuous optical excitation and mw frequency sweeps[14,15]
Since the spin dynamics is insensitive to the exact start and end magnetic field values, the results in Fig. 1 indicate that P1-assisted DNP can be made robust to field heterogeneities

Summary

Introduction

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. . The upper and lower inserts highlight the impact of P1 spin-lattice relaxation throughout the DNP cycle in (a) for the limit cases where one field ramp is much faster than the other one; for simplicity, we collapse the NV–P1–1H energy diagrams to sets of four horizontal lines, each corresponding to the branch in Fig. 1d with the same color code.

Results

Conclusion