Dynamics of tunneling into nonequilibrium edge states

Time-dependent perturbations can drive a trivial two-dimensional band insulator into a quantum Hall-like phase, with protected nonequilibrium states bound to its edges. We propose an experiment to probe the existence of these topological edge states which consists of passing a tunneling current through a small two-dimensional sample out of equilibrium. The signature is a nonquantized metallic conductance near the edges of the sample and, in contrast, an excitation gap in the bulk. This proposal is demonstrated for the case of a two-dimensional lattice model of Dirac electrons with tunable mass in a strong electromagnetic field. In addition, we also study the tunneling conductance of the driven resonant level model and find a phenomenon similar to dynamic localization in which certain transport channels are suppressed.