Vortex states in nanosuperconductor

The vortex states in nanoscale superconductors are investigated within generalized Bogolubov-de Gennes theory. For symmetric (square-shaped) samples thermodynamically stable vortex phases form symmetry-consistent patterns and no transition to conventional Abrikosov-like vortex patterns occurs till T = 0K for sizes not exceeding 25 nm. For vorticity $L = 2$ a giant vortex is stabilized at temperatures in the vicinity of T$_c$, which transforms into a giant antivortex $L = -2$ and four normal vortices with lowering the temperature. On the other hand, the vortex pattern for vorticity $L = 3$ corresponds to an antivortex $L = -1$ and four normal vortices in the whole temperature domain.