New Universality Class at the Superconductor-Insulator Transition

We study transport properties of thin films near the superconductor-insulator transition. Formulated in a phase representation, the key new feature of our model is the assumption of a local Ohmic dissipative mechanism. Coarse graining leads to a Ginzburg-Landau description, with non-Ohmic dynamics for the order parameter. For strong enough damping a new universality class is found. It is characterized by a nonuniversal dc conductivity, and a damping-dependent dynamical critical exponent. The formulation also provides a description of the magnetic-field-tuned transition. Several microscopic mechanisms are proposed as the origin of the dissipation.