Thermodynamics of a vortex system in a thin superconducting film with radiation defects

The effect of radiation defects on the thermodynamics of a system of Pearl vortices in a thin superconducting film is examined. The scenario for a Kosterlitz-Thouless transition in this system is shown to depend on the defect concentration nd. At low concentrations, the transition takes place continuously, while at high concentrations, a range of temperatures exists in which there are two metastable states. The concentrations of free vortices and of vortices captured by defects are calculated as functions of temperature for different defect concentrations nd. A phase diagram is constructed for the vortex system in the nd−T plane.