Observation of Photonic Topological Floquet Time Crystals

The two main research questions on time crystals are: What is a time crystal? Is there a material that is spontaneously crystalline in time? This study synthesizes a photonic material of topological Floquet time crystals and experimentally observes its indicative period‐ beating. A single‐particle picture is explicitly reconstructed of discrete time‐crystalline phase and is revealed using an appropriately‐designed photonic Floquet simulator the rigid period‐doubling as a signature of the breakage of the discrete time‐translational symmetry. Unlike the requirement of the many‐body localization, the photonic Floquet time crystal is derived from a newly defined single‐particle topological phase that can be extensively accessed by many pertinent nonequilibrium and periodically‐driven platforms. The observation will drive theoretical and technological interests toward condensed matter physics and topological photonics.