Optical polarization of nuclear ensembles in diamond

TL;DR

This paper demonstrates high polarization of nuclear spins in diamond using electron spin transfer from nitrogen vacancy centers, with polarization dependent on magnetic field and temperature, relevant for quantum and sensing applications.

Contribution

It introduces a method to polarize nuclear spins in diamond via electron spin transfer at excited-state level anti-crossing, achieving high polarization levels.

Findings

90% polarization of 14N nuclear spins in NV centers

70% polarization of proximal 13C nuclear spins

High polarization persists down to 50 K

Abstract

We report polarization of a dense nuclear-spin ensemble in diamond and its dependence on magnetic field and temperature. The polarization method is based on the transfer of electron spin polarization of negatively charged nitrogen vacancy color centers to the nuclear spins via the excited-state level anti-crossing of the center. We polarize 90% of the 14N nuclear spins within the NV centers, and 70% of the proximal 13C nuclear spins with hyperfine interaction strength of 13-14 MHz. Magnetic-field dependence of the polarization reveals sharp decrease in polarization at specific field values corresponding to cross-relaxation with substitutional nitrogen centers, while temperature dependence of the polarization reveals that high polarization persists down to 50 K. This work enables polarization of the 13C in bulk diamond, which is of interest in applications of nuclear magnetic resonance, in quantum memories of hybrid quantum devices, and in sensing.