Magnetic skyrmions and their lattices in triplet superconductors

A complete topological classification of solutions in SO(3) symmetric Ginzburg-Landau free energy has been performed and a new class of solutions in weak external magnetic field carrying two units of magnetic flux has been identified. These solutions, magnetic skyrmions, do not have a singular core as Abrikosov vortices do and at low magnetic field they become lighter for strongly type II superconductors. As a consequence, the lower critical magnetic field Hc1 is reduced by a factor of lnκ. Magnetic skyrmions repel each other as $1/r$ at distances much larger than magnetic penetration depth λ forming a relatively robust triangular lattice. Magnetization near Hc1 increases gradually as (H-Hc1)². This behavior agrees very well with experiments on heavy fermion superconductor UPt₃. Newly discovered Ru based compounds Sr₂RuO₄ and Sr₂YRu_1-xCuₓO₆ are other possible candidates to possess skyrmion lattices. Deviations from exact SO(3) symmetry are also studied.