Realization of an inherent time crystal in a dissipative many-body system

TL;DR

This paper demonstrates the theoretical prediction and experimental realization of an inherent time crystal in a dissipative many-body system, showing spontaneous continuous time translation symmetry breaking without external periodic forcing.

Contribution

It provides the first evidence of a self-sustained, inherent time crystal arising from many-body interactions, both theoretically and experimentally, in a dissipative atomic system.

Findings

Spontaneous breaking of continuous time translation symmetry in a many-body system.

Observation of self-protected periodic motion in erbium-doped solid.

Measured coherence time exceeds that of individual ions.

Abstract

Time crystals are many-body states that spontaneously break translation symmetry in time the way that ordinary crystals do in space. While experimental observations have confirmed the existence of discrete or continuous time crystals, these realizations have relied on the utilization of periodic forces or effective modulation through cavity feedback. The original proposal for time crystals is that they would represent self-sustained motions without any external periodicity, but realizing such purely self-generated behavior has not yet been achieved. Here, we provide theoretical and experimental evidence that many-body interactions can give rise to an inherent time crystalline phase. Following a calculation that shows an ensemble of pumped four-level atoms can spontaneously break continuous time translation symmetry, we observe periodic motions in an erbium-doped solid. The inherent time crystal produced by our experiment is self-protected by many-body interactions and has a measured coherence time beyond that of individual erbium ions.