Probing dynamics of an electron-spin ensemble via a superconducting resonator

TL;DR

This study investigates the spin relaxation and diffusion dynamics of nitrogen impurity electron spins in diamond at low temperatures using a superconducting resonator, revealing insights into spin diffusion and cross-relaxation effects.

Contribution

It provides new experimental insights into spin relaxation, diffusion, and cross-relaxation in nitrogen impurity ensembles in diamond at cryogenic temperatures.

Findings

Spin linewidth and relaxation time are temperature-independent.

Spin diffusion limits the relaxation process.

Fast cross-relaxation occurs between sub-ensembles.

Abstract

We study spin relaxation and diffusion in an electron-spin ensemble of nitrogen impurities in diamond at low temperature (0.25-1.2 K) and polarizing magnetic field (80-300 mT). Measurements exploit mode- and temperature-dependent coupling of hyperfine-split sub-ensembles to the resonator. Temperature-independent spin linewidth and relaxation time suggest that spin diffusion limits spin relaxation. Depolarization of one sub-ensemble by resonant pumping of another indicates fast cross-relaxation compared to spin diffusion, with implications on use of sub-ensembles as independent quantum memories.