Electromagnetic interaction of vortices in layered superconducting structures

A multilayered superconducting system with a purely electromagnetic coupling between layers is considered. A general formula is derived for the energy of an arbitrary configuration of point vortices localized in the layers. It is shown that the interaction energy of a vortex and an antivortex located on the same layer depends logarithmically on their distance for large distances. The structure of a vortex line in perpendicular fields is also considered. Two different regimes appear, depending on the ratio of the interlayer distance d to the effective one-layer screening length λ eff = λ 2L/ d0 where λL is the London screening length in the layers and do the layer thickness. Due to the temperature dependence of λL, the behaviour of the first critical field H c1 is expected to show a crossover below Tc.