Suppression of superconductivity in mesoscopic superconductors

We propose a new boundary-driven phase transition associated with vortex nu cleation in mesoscopic superconductors (of size of the order of, or larger than, the penetration depth). We derive the rescaling equations and we show that boundary effects associated with vortex nucleation lower the conventi onal transition temperature in mesoscopic superconductors by an amount whic h is a function of the size of the superconductor. This result explains rec ent experiments in small superconductors where it was found that the transi tion temperature depends on the size of the system and is lower than the cr itical Berezinski-Kosterlitz-Thouless temperature. DOI: 10.1103/PhysRevLett .86.716.