Vortex states in nanosuperconductors

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. The main features of Ginzburg-Landau phase diagram are confirmed. [1] B. Deloof, V.V. Moshchalkov, L.F. Chibotaru, Ann. Phys. 1-6 (2013)/DOI 10-.1002.