Emergent Universal Quench Dynamics in Randomly Interacting Spin Models

TL;DR

This paper reports the experimental discovery of universal behavior in the non-equilibrium spin depolarization dynamics of a solid-state NMR system with random interactions, revealing universality beyond low-energy physics.

Contribution

It provides the first experimental evidence of universal dynamics in high-temperature, far-from-equilibrium quantum many-body systems with random interactions.

Findings

Correlation functions follow a universal functional form

Dominant processes leading to universality are identified

Universality extends to high-temperature non-equilibrium dynamics

Abstract

Universality often emerges in low-energy equilibrium physics of quantum many-body systems, despite their microscopic complexity and variety. Recently, there has been a growing interest in studying far-from-equilibrium dynamics of quantum many-body systems. Such dynamics usually involves highly excited states beyond the traditional low-energy theory description. Whether universal behaviors can also emerge in such non-equilibrium dynamics is a central issue at the frontier of quantum dynamics. Here we report the experimental observation of universal dynamics by monitoring the spin depolarization process in a solid-state NMR system described by an ensemble of randomly interacting spins. The spin depolarization can be related to temporal spin-spin correlation functions at high temperatures. We discover a remarkable phenomenon that these correlation functions obey a universal functional form. This experimental fact helps us identify the dominant interacting processes in the spin depolarization dynamics that lead to this universality. Our observation demonstrates the existence of universality even in non-equilibrium dynamics at high temperatures, thereby complementing the well-established universality in low-energy physics.