Fundamental Electromagnetic Phenomena in Superconductors

Abstract

Here we assume a sufficiently large superconductor. When a magnetic field is applied to the superconductor, flux lines penetrate it from the surface. Since the flux lines are expected to be pinned by pinning centers in the superconductor, those cannot penetrate deeply from the surface and the density of the flux lines will be higher near the surface and lower in the inner region, resulting in a nonuniform distribution in a macroscopic scale. When the external magnetic field is decreased, on the other hand, the flux lines go out of the superconductor and their density becomes lower near the surface. It is important to know correctly the magnetic flux distribution in the superconductor in such cases in order to understand or foresee its electromagnetic phenomenon exactly.