Influence of the paramagnetic effect on the vortex lattice in 2D superconductors

In 2D superconductors under a high magnetic field, when the upper critical field H-c2 is determined by both the orbital and paramagnetic effects, new solutions for the superconducting order parameter, corresponding to higher Landau levels: must be realized. In order to determine the structure of the vortex lattice in the new phases, we derive a modified Ginzburg-Landau fun ctional in the high-k limit. Within this model, we show that the stability of the structures depends on a new criterion which replaces the Abrikosov p arameter beta(A). The triangular lattice is not always favored. We calculat e the most favorable structures at different temperatures, and we find chan ges of the symmetry, as well as the transition order.