Structures of single vortex and vortex lattice in a d-wave superconductor

The structures of a single vortex and vortex lattice in a superconductor with d(x2-y2) symmetry are studied self-consistently employing a recently developed Ginzburg-Landau theory. Near a single vortex, we found that an s-wave component of the order parameter is always induced, and it causes the local magnetic-field distribution and the d-wave order parameter to have a fourfold anisotropy. It is shown that there is a strong correlation between the structure of a single vortex and the shape of the vortex lattice. Our numerical calculation indicates that the structure of the vortex lattice is always oblique except for temperatures very close to T-c where it becomes triangular. The possible connection of the result with experiment is also discussed.