Transport across an impurity in one-dimensional quantum liquids far from equilibrium

We study the effect of a single impurity on the transport properties of a one-dimensional quantum liquid highly excited away from its ground state by a sudden quench of the bulk interaction. In particular we compute the time-dependent dc current to leading order in the impurity potential, using bosonization and starting both from the limit of a uniform system and from the limit of two decoupled semi-infinite systems. Our results reveal that the nonequilibrium excitation of bulk modes induced by the global quench has important effects on the conductor-insulator quantum phase transition, turning it into a crossover for any small quench amplitude and destroying the exact duality between the conducting and insulating fixed points. In addition, the current displays a faster decay towards the steady state than the equilibrium case, a signature of quench-induced decoherence.