The problem of nonlinear transport near a quantum phase transition is solved within the Landau theory for the dissipative insulator-superconductor phase transition in two dimensions. Using the nonequilibrium Schwinger round-trip Green function formalism, we obtain the scaling function for the nonlinear conductivity in the quantum-disordered regime. We find that the conductivity scales as $E^2$ at low fields but crosses over at large fields to a universal constant on the order of $e^2/h$. The crossover between these two regimes obtains when the length scale for the quantum fluctuations becomes comparable to that of the electric field within logarithmic accuracy.

• Received 7 October 2003

DOI:https://doi.org/10.1103/PhysRevLett.93.027004