Dynamics and universality in noise-driven dissipative systems

We investigate the dynamical properties of low-dimensional systems, driven by external noise sources. Specifically we consider a resistively shunted Josephson junction and a one-dimensional quantum liquid in a commensurate lattice potential, subject to 1/f noise. In absence of nonlinear coupling, we have shown previously that these systems establish a nonequilibrium critical steady state [Dalla Torre, Demler, Giamarchi, and Altman, Nat. Phys. 6, 806 (2010)]. Here, we use this state as the basis for a controlled renormalization group analysis using the Keldysh path integral formulation to treat the nonlinearities: the Josephson coupling and the commensurate lattice. The analysis to first order in the coupling constant indicates transitions between superconducting and localized regimes that are smoothly connected to the respective equilibrium transitions. However, at second order, the back action of the mode coupling on the critical state leads to renormalization of dissipation and emergence of an effective temperature. In the Josephson junction, the temperature is parametrically small allowing to observe a universal crossover between the superconducting and insulating regimes. The I-V characteristics of the junction displays algebraic behavior controlled by the underlying critical state over a wide range. In the noisy one-dimensional liquid, the generated dissipation and effective temperature are not small as in the junction. We find a crossover between a quasilocalized regime dominated by dissipation and another dominated by temperature. However, since in the thermal regime the thermalization rate is parametrically small, signatures of the nonequilibrium critical state may be seen in transient dynamics.