The break-up of the vortex structure in a mesoscopic wire containing a constriction

Within the nonlinear Ginzburg-Landau theory, we study the superconducting state in a mesoscopic wire containing a narrow constriction in the presence of a uniform magnetic field directed along the wire. If the narrow region is small enough so that no vortices can penetrate through it, curved vortices are formed, i.e. they enter at the top of the sample ( the widest part) and exit near the constriction. At high magnetic fields a giant vortex is nucleated in the widest part of the wire which breaks up into a smaller giant and/or individual vortices near the constriction.