Photonic Floquet time crystals

TL;DR

This paper reports the synthesis and experimental observation of photonic Floquet time crystals, demonstrating spontaneous time-translational symmetry breaking through period-doubling in a single-particle topological phase.

Contribution

It introduces a photonic platform for realizing Floquet time crystals and provides experimental evidence of their characteristic period-doubling behavior.

Findings

Observation of period-2T beating in photonic Floquet systems

Reconstruction of a discrete time-crystalline ground state

Identification of topological phase as the basis for time crystal behavior

Abstract

The public and scientists constantly have different perspectives. While on a time crystal, they stand in line and ask: What is a time crystal? Show me a material that is spontaneously crystalline in time? This study synthesizes a photonic material of Floquet time crystals and experimentally observes its indicative period-2T beating. We explicitly reconstruct a discrete time-crystalline ground state and reveal using an appropriately-designed photonic Floquet simulator the rigid period-doubling as a signature of the spontaneous breakage of the discrete time-translational symmetry. Unlike the result of the exquisite many-body interaction, the photonic time crystal is derived from a single-particle topological phase that can be extensively accessed by many pertinent nonequilibrium and periodically-driven platforms. Our observation will drive theoretical and technological interests toward condensed matter physics and topological photonics, and demystify time crystals for the non-scientific public.