Vortex structures in a mesoscopic unconventional superconductors*

We investigate the vortex structures in unconventional superconductors of mesoscopic size. It is well-known that, in such small systems, the size as well as the shape have a profound influence on the formation of the vortex structure, leading to interesting phenomena such as giant vortex and anti-vortex. We present unusual vortex structures when the order parameters are unconventional and multi-dimensional. Especially, we focus on the vortex structures in mesoscopic unconventional superconductors. The results are compared with those in conventional ones. For concreteness, the order parameter which transforms according to the E_1g representation of D_6h is chosen. The vortex structures are obtained by minimizing the Ginzburg-Landau free energy, using the simulated annealing method.