Enhancement of nuclear spin coherence times by driving dynamic nuclear polarization at defect centers in solids

TL;DR

This paper presents a theoretical model showing that dynamic nuclear polarization (DNP) driven at defect centers in solids can significantly enhance nuclear spin coherence times, potentially improving quantum sensing and imaging applications.

Contribution

The study develops a microscopic theory linking DNP driving time to increased nuclear spin coherence times, providing insights for experimental enhancement of quantum coherence.

Findings

Nuclear spin coherence times can be increased by several orders of magnitude through DNP.

Theoretical results align with experimental observations of relaxation time enhancements.

Driving time is a key factor influencing the extent of coherence time improvement.

Abstract

The hyperpolarization of nuclear spins can enable powerful imaging and sensing techniques provided the hyperpolarization is sufficiently long-lived. Recent experiments on nanodiamond $^{13}$C nuclear spins demonstrate that relaxation times can be extended by three orders of magnitude by building up dynamic nuclear polarization (DNP) through the driving of electron-nuclear flip-flop processes at defect centers. This finding raises the question of whether the nuclear spin coherence times are also impacted by this hyperpolarization process. Here, we theoretically examine the effect of DNP on the nuclear spin coherence times as a function of the hyperpolarization drive time. We do this by developing a microscopic theory of DNP in a nuclear spin ensemble coupled to microwave-driven defect centers in solids and subject to spin diffusion mediated by internuclear dipolar interactions. We find that, similarly to relaxation times, the nuclear spin coherence times can be increased substantially by a few orders of magnitude depending on the driving time. Our theoretical model and results will be useful for current and future experiments on enhancing nuclear spin coherence times via DNP.