Superconducting transition induced by columnar disorder in strong magnetic field

Abstract

The superconducting transition in presence of strong columnar disorder parallel to the magnetic field is considered. A solvable model appropriate for description of the broad crossover regime towards the true "glassy" critical behavior is constructed, and the behavior of the thermodynamic quantities and of the Edwards-Anderson order-parameter is obtained. The critical exponents for the correlation lengths orthogonal and parallel to the magnetic field are equal and in agreement with the experimental values. The dynamical critical exponent is $z=2$, also in agreement with the measured value. Several perturbations to the solvable model are considered and shown to be irrelevant for the critical behavior. It is argued that there exists an optimal density of defects at which the transition temperature at given magnetic field reaches its maximum.