Glassy dynamics in a disordered Heisenberg quantum spin system

TL;DR

This paper observes glassy, sub-exponential relaxation dynamics in a disordered quantum spin system, revealing non-classical correlations and disorder-independent relaxation up to a critical point, advancing understanding of quantum glassy phases.

Contribution

It demonstrates anomalous quantum relaxation dynamics in a disordered XXZ spin system, linking classical glassy behavior to quantum correlations and disorder effects.

Findings

Sub-exponential relaxation of magnetization observed

Relaxation dynamics are disorder-independent below a critical disorder strength

Quantum correlations drive glassy relaxation behavior

Abstract

Understanding the dynamics of strongly interacting disordered quantum systems is one of the most challenging problems in modern science, due to features such as the breakdown of thermalization and the emergence of glassy phases of matter. We report on the observation of anomalous relaxation dynamics in an isolated XXZ quantum spin system realized by an ultracold gas of atoms initially prepared in a superposition of two-different Rydberg states. The total magnetization is found to exhibit sub-exponential relaxation analogous to classical glassy dynamics, but in the quantum case this relaxation originates from the build-up of non-classical correlations. In both experiment and semi-classical simulations, we find the evolution towards a randomized state is independent of the strength of disorder up to a critical value. This hints towards a unifying description of relaxation dynamics in disordered isolated quantum systems, analogous to the generalization of statistical mechanics to out-of-equilibrium scenarios in classical spin glasses.