Observation of Photonic Topological Floquet Time Crystals

Abstract

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- (Formula presented.) 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.