The Anomalous Floquet Insulator
Abstract: In recent years, periodic driving has been studied intensively as a means for driving otherwise ordinary systems into exotic topological phases. This has led to discoveries of new, so-called anomalous phases, which can only exist in periodically driven systems; the Floquet time crystal is one prominent example.
Here we demonstrate the existence of another such anomalous phase: the anomalous Floquet insulator (AFI). The AFI is a new phase, induced by periodic driving in strongly disordered two-dimensional systems. The nontrivial topological properties of the AFI give rise to a quantized current at the edge, and quantized orbital magnetization in the bulk. These effects are of intrinsically nonequilibrium nature and have no counterpart in equilibrium systems. The results presented here strongly suggest that the AFI remains a stable phase in the presence of interactions, due to disorder-induced many-body localization.