Exploring Localization in Nuclear Spin Chains

TL;DR

This paper introduces a new correlation metric to distinguish many-body localization from Anderson localization in high-temperature spin systems, demonstrated using nuclear magnetic resonance techniques to observe localization phenomena.

Contribution

The authors develop and experimentally validate a novel correlation metric capable of differentiating MBL from AL in solid-state spin systems, advancing localization detection methods.

Findings

Correlation metric saturates for AL, increases logarithmically for MBL

Localization observed in natural solid-state spin systems via NMR

Simulations confirm the metric's behavior aligns with entanglement entropy patterns

Abstract

Characterizing out-of-equilibrium many-body dynamics is a complex but crucial task for quantum applications and the understanding of fundamental phenomena. A central question is the role of localization in quenching quantum thermalization, and whether localization survives in the presence of interactions. The localized phase of interacting systems (many-body localization, MBL) exhibits a long-time logarithmic growth in entanglement entropy that distinguishes it from the noninteracting Anderson localization (AL), but entanglement is difficult to measure experimentally. Here, we present a novel correlation metric, capable of distinguishing MBL from AL in high-temperature spin systems. We demonstrate the use of this metric to detect localization in a natural solidstate spin system using nuclear magnetic resonance (NMR). We engineer the natural Hamiltonian to controllably introduce disorder and interactions and observe the emergence of localization. In particular, while our correlation metric saturates for AL, it keeps increasing logarithmically for MBL, a behavior reminiscent of entanglement entropy, as we confirm by simulations. Our results show that our NMR techniques, akin to measuring out-of-time correlations, are well suited for studying localization in spin systems.