Universal Long-time Behavior of Nuclear Spin Decays in a Solid

TL;DR

This study demonstrates that nuclear spin decays in solids, regardless of initial conditions, converge to a universal long-time behavior characterized by sinusoidally modulated exponential decay, revealing fundamental insights into statistical physics limits.

Contribution

The paper provides experimental evidence of a universal long-time decay behavior in nuclear spins, extending understanding beyond conventional statistical physics approximations.

Findings

Different initial configurations lead to the same long-time decay behavior.

Long-time decay exhibits sinusoidally modulated exponential form.

Universality aligns with predictions based on classical chaotic system resonances.

Abstract

Magnetic resonance studies of nuclear spins in solids are exceptionally well suited to probe the limits of statistical physics. We report experimental results indicating that isolated macroscopic systems of interacting nuclear spins possess the following fundamental property: spin decays that start from different initial configurations quickly evolve towards the same long-time behavior. This long-time behavior is characterized by the shortest ballistic microscopic timescale of the system and therefore falls outside of the validity range for conventional approximations of statistical physics. We find that the nuclear free induction decay and different solid echoes in hyperpolarized solid xenon all exhibit sinusoidally modulated exponential long-time behavior characterized by identical time constants. This universality was previously predicted on the basis of analogy with resonances in classical chaotic systems.