Numerical investigation of critical states in superposed superconducting films

peer reviewedThis paper examines the magnetic field and supercurrent distributions in three-dimensional (3D) structures made of superposed superconducting films. A recent experimental study of such structures (Tamegai et al 2017 Physica C 533 74–910) has shown unusual patterns of the trapped magnetic flux, with an unexpected discontinuity line in the region where the films overlap. In this work, a finite element model is used to reproduce and understand these patterns. It is shown that the newly observed discontinuity line originates from the magnetic field dependence of the critical current density. Moreover, in contrast to common observations made in planar superconducting structures, the network of critical lines is found to evolve with the applied field when the 3D structure is magnetized after zero-field cooling. These findings underline the importance of the magnetic coupling between the components of a multi-layered superconducting structure in building its critical state.ARC 13/18-0