Crossover between types I and II in diffusive superconductors: Perturbative study

A common feature of both single- and multiband superconductors is the presence of a crossover between conventional type I and type II superconductivity through an intertype (IT) domain in the phase diagram of the magnetic response. In diffusive single-band superconductors, this domain is known to be very narrow due to scattering by nonmagnetic impurities. Recently, it has been shown that in multiband superconductors the IT domain can significantly expand when the band diffusion coefficients differ substantially. In this paper, we demonstrate that this expansion is a general feature of diffusive multiband superconductors and is accompanied by a qualitative change in vortex-vortex interaction. This interaction shifts from the combination of short-range attraction and long-range repulsion, typical of diffusive single-band IT superconductors, to the inverse configuration of short-range repulsion and long-range attraction. Strikingly, this latter behavior resembles the vortex interaction in clean IT superconductors. Consequently, one can expect a corresponding rearrangement of vortex configurations---from the mixtures of Abrikosov and giant vortices, expected in diffusive single-band IT superconductors, to vortex chains, labyrinths, and clusters, which are characteristic of vortex matter in clean IT superconducting materials.