Vortex states of the Eu model for Sr2RuO4

Based on the Ginzburg-Landau functional of E-u symmetry presented by Agterberg, vortex states of Sr2RuO4 are studied in detail over H-c1 less than or similar to H less than or equal to H-c2 by using the Landau-level expansion method. For the field in the basal plane, it is found that (i) the second superconducting transition should be present irrespective of the field direction, (ii) below this transition, a characteristic double-peak structure may develop in the magnetic-field distribution, and (iii) a third transition may occur between two different vortex states. It is also found that, when the held is along the c axis, the square vortex lattice may deform through a second-order transition into a rectangular one as the field is lowered from H-c2.