Superconducting films in perpendicular fields and the effect of the de Gennes parameter

Abstract

In this paper we study superconductivity of a thin film placed in a perpendicular magnetic field. We discuss the dependence of the upper critical field HC3 on the thickness l of the film and the Ginzburg-Landau parameter κ, and we examine nucleation of superconductivity. We show that a critical change occurs at l = 2γκ-2. If l > aκ-2 (a > 2γ), the film exhibits type II behaviors: as the applied magnetic field decreases from HC3, superconductivity nucleates in a strip at the lateral surface and develops a lateral surface superconducting state. If l ≤ 2γκ-2 + Cκ-4, the film exhibits type I behaviors.