Localization, Topology, and Quantized Transport in Disordered Floquet Systems

We investigate the effects of disorder on a periodically driven one-dimensional model displayingquantized topological transport. We show that, while instantaneous eigenstates are necessarily Andersonlocalized, the periodic driving plays a fundamental role in delocalizing Floquet states over the wholesystem, henceforth allowing for a steady-state nearly quantized current. Remarkably, this is linked to alocalization-delocalization transition in the Floquet states at strong disorder, which occurs for periodicdriving corresponding to a nontrivial loop in the parameter space. As a consequence, the Floquet spectrumbecomes continuous in the delocalized phase, in contrast with a pure-point instantaneous spectrum.