The statistical mechanics of vortex system in thin superconducting film in cycle approximation. III. Finite size vortex core effects

The statistical mechanics of vortex system in two-dimensional superconductor is discussed in the frame of the cycle approximation. The finite size of vortex core and vortex core shape are taken into account. This effect leads to the crossover of the vortex–antivortex pair unbinding transition from the usual continuous Kosterlitz–Thouless-like behavior for large core energies to the first order transition for low energies.