Observation of Floquet prethermalization in dipolar spin chains

TL;DR

This paper reports the experimental observation of Floquet prethermalization in dipolar spin chains, demonstrating long-lived non-equilibrium states and confirming the exponential suppression of heating at high frequencies.

Contribution

First experimental demonstration of Floquet prethermalization in dipolar spin chains using NMR, confirming theoretical predictions of slow heating and quasi-conservation laws.

Findings

Observation of long-lived prethermal states

Confirmation of exponential slow heating rate

Persistence of quasi-conservation laws beyond effective Hamiltonian regime

Abstract

Periodically driven Floquet quantum systems provide a promising platform to investigate novel physics out of equilibrium. Unfortunately, the drive generically heats up the system to a featureless infinite temperature state. For large driving frequency, the heat absorption rate is predicted to be exponentially small, giving rise to a long-lived prethermal regime which exhibits all the intriguing properties of Floquet systems. Here we experimentally observe Floquet prethermalization using nuclear magnetic resonance techniques. We first show the relaxation of a far-from-equilibrium initial state to a long-lived prethermal state, well described by the time-independent ''prethermal'' Hamiltonian. By measuring the autocorrelation of this prethermal Hamiltonian we can further experimentally confirm the predicted exponentially slow heating rate. More strikingly, we find that in the timescale when the effective Hamiltonian picture breaks down, the Floquet system still possesses other quasi-conservation laws. Our results demonstrate that it is possible to realize robust Floquet engineering, thus enabling the experimental observation of non-trivial Floquet phases of matter.