Speedup of nuclear-spin diffusion in hyperpolarized solids

TL;DR

This paper introduces a correction factor to nuclear-spin diffusion coefficients that accounts for hyperpolarization, showing that diffusion accelerates with increased polarization, impacting nuclear polarization buildup.

Contribution

The paper extends Lowe-Gade theory to low-temperature, high-polarization regimes, providing a new correction factor for nuclear-spin diffusion.

Findings

Diffusion accelerates with increased nuclear polarization.

Correction factor approaches unity at low polarization.

Implications for dynamic nuclear polarization processes.

Abstract

We propose a correction to the coefficient of nuclear-spin diffusion by a factor $1/\sqrt{1-\overline{p}^{2}}$, where $\overline{p}$ is the average nuclear-spin polarization. The correction, derived by extending the Lowe-Gade theory to low-temperature cases, implies that transportation of nuclear magnetization through nuclear-spin diffusion accelerates when the system is hyperpolarized, whereas for low-polarization the correction factor approaches unity and the diffusion coefficient coincides with the conventional diffusion coefficient valid in the high-temperature limit. The proposed scaling of the nuclear-spin diffusion coefficient can lead to observable effects in the buildup of nuclear polarization by dynamic nuclear polarization.