Vortex structure for a d+is-wave superconductor

The uniform phase, the single vortex structure, and the vortex lattice structure of a d + is-wave superconductor are studied numerically by simulating the Ginzburg-Landau equations with the finite-element method. In the uniform phase, for superconductors with attractive interactions in both the s- and the d-wave channels, there exists a certain range of che relative strength of interactions (or temperatures) such that a df is state is stable while at other regions only a d-wave state is stable. More strikingly, the s- and d-wave components of a single vortex in the d + is state exhibit twofold symmetry. The relative phase between these two components is roughly pi/2 for the d + is-wave state. In the d-dominant phase, as the magnetic field increases, the impact of the s-wave component on the energy gap can be more significant. The vortex structure changes from a square to an oblique, and finally to a triangular lattice with decreasing s-wave channel interaction (or increasing temperature). [S0163-1829(99)01701-4].