Observation of a space-time crystal in a superfluid quantum gas

TL;DR

This paper reports the first direct observation of a space-time crystal in a superfluid quantum gas, demonstrating spontaneous breaking of discrete symmetries in both space and time, and opening avenues for exploring new nonequilibrium phases.

Contribution

It provides the first experimental evidence of a space-time crystal in a superfluid quantum gas with direct imaging and theoretical understanding.

Findings

Direct visualization of space-time periodic structure

Spontaneous breaking of discrete space-time symmetry

Theoretical description confirming the mechanism

Abstract

Time crystals are a phase of matter, for which the discrete time symmetry of the driving Hamiltonian is spontaneously broken. The breaking of discrete time symmetry has been observed in several experiments in driven spin systems. Here, we show the observation of a space-time crystal using ultra-cold atoms, where the periodic structure in both space and time are directly visible in the experimental images. The underlying physics in our superfluid can be described ab initio and allows for a clear identification of the mechanism that causes the spontaneous symmetry breaking. Our results pave the way for the usage of space-time crystals for the discovery of novel nonequilibrium phases of matter.