Nonequilibrium many-body quantum engine driven by time-translation symmetry breaking

TL;DR

This paper explores a many-body quantum engine that leverages nonequilibrium phase transitions and time-crystalline phases to generate mechanical work, revealing new possibilities for quantum machine design.

Contribution

It introduces a theoretical model of a quantum engine driven by time-translation symmetry breaking, including the novel finding that it can operate without periodic driving.

Findings

Engine produces work under periodic driving.

Phase transitions cause abrupt changes in work output.

Engine can operate in a time-crystalline phase without driving.

Abstract

Quantum many-body systems out of equilibrium can host intriguing phenomena such as transitions to exotic dynamical states. Although this emergent behaviour can be observed in experiments, its potential for technological applications is largely unexplored. Here, we investigate the impact of collective effects on quantum engines that extract mechanical work from a many-body system. Using an opto-mechanical cavity setup with an interacting atomic gas as a working fluid, we demonstrate theoretically that such engines produce work under periodic driving. The stationary cycle of the working fluid features nonequilibrium phase transitions, resulting in abrupt changes of the work output. Remarkably, we find that our many-body quantum engine operates even without periodic driving. This phenomenon occurs when its working fluid enters a phase that breaks continuous time-translation symmetry: the emergent time-crystalline phase can sustain the motion of a load generating mechanical work. Our findings pave the way for designing novel nonequilibrium quantum machines.