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We study the vortex profiles in two-gap superconductors using the extended Ginzburg-Landau theory. The results shed more light on the disparity between the effective length scales in two bands. We compare the behavior expected from the standard Ginzburg-Landau theory with this new approach, and find good qualitative agreement in the case of LiFeAs. (C) 2011 Elsevier B.V. All rights reserved.

We performed a molecular dynamics study of vortex-antivortex motion in a superconducting disk with a magnetic dot on top, in the Corbino disk geometry. In this system, vortices and antivortices are forced to move in opposite azimuthal directions by a radially applied current. The dot is magnetized out of plane in order to stabilize composite vortex-antivortex configurations, with vortices closer to the center of the disk and antivortices near to the disk edge. We observe that the interplay between the spatially inhomogeneous current distribution, the screening currents induced by the dipole, and the attractive vortex-antivortex (v-av) interaction result in different dynamical phases. At low current values, antivortices which are distributed at outer rings - remain bounded to vortices at inner rings and the whole configuration rotates rigidly. Above a threshold current, vortices and antivortices unbind and move at different angular velocities in a highly correlated way. Finally, at very strong drive, vortex-antivortex attraction is overhelmed by the external current Lorentz force, causing them to move in opposite directions. (C) 2011 Elsevier B.V. All rights reserved.

Within the phenomenological Ginzburg–Landau (GL) theory, we investigate the vortex structure of a thin superconducting film (SC) with a regular matrix of ferromagnetic dots (FD) deposited on top of it. The vortex pinning properties of such a magnetic lattice are studied, and the field polarity dependent votex pinning is observed. The exact vortex configuration depends on the size of the magnetic dots, their polarity, periodicity of the FD-rooster and the properties of the SC expressed through the effective Ginzburg–Landau parameter κ * .

For a superconducting film with regular array of antidots, we constructed the equilibrium vortex phase diagram within the Ginzburg–Landau (GL) formalism. Novel ground-state vortex configurations were found depending on the size and periodicity of the antidots and the GL parameter κ , comprising vortex–antivortex structures, giant- and multi-vortex combinations, or lattices of giant-vortices, all commensurate with the square pinning arrays.

We experimentally study a triangular, micrometer-sized Pb single crystal through ballistic Hall micro-probe magnetometry. This mesoscopic system allows an easy adjustment of the maximum accomodated fluxoid state by tuning the temperature. Magnetization loops of the type-I superconductor were measured at various temperatures up to T c = 7.18 K. We observe several novel features, including mestastable fluxoid states and changes in the normal-to-superconducting transition mechanism with temperature.