SUPERCONDUCTOR-INSULATOR TRANSITION WITH NONUNIVERSAL CONDUCTIVITY

Motivated by experimental evidence for the importance of fermionic deg rees of freedom near the superconductor-insulator transition, we take into account gapless electronic excitations for the description of the transition. Integrating them out yields a damping for the phase of th e superconducting grains. We derive a Ginzburg-Landau-Wilson descripti on for the onset of superfluidity which shows a non-ohmic dynamics. Th is dynamics depends qualitatively on the strength of the damping. Suff iciently strong damping modifies both, the critical behavior and the r esponse near the transition. The critical exponents depend on the damp ing strength. The conductivity at the transition is finite but non-uni versal.