Flux penetration in slab-shaped type-I superconductors

We study the problem of flux penetration into type-I superconductors with a high demagnetization factor (slab geometry). We analyze the process by which flux invades the sample as the applied held is increased slowly from zero, concentrating on the role of demagnetization. We find that flux does not penetrate gradually. Rather there is an instability in the process and the flux penetrates from the boundary in a series of bursts, accompanied by the formation of isolated droplets of the normal phase, leading to a multiply connected flux-domain structure similar to what is seen in experiments.