GINZBURG-LANDAU EQUATIONS AND STRUCTURES OF VORTICES IN A SUPERCONDUCTOR WITH D(X)2(-Y)2 SYMMETRY

The structures of a single vortex and vortex lattice in a superconduct or with d(x)2(-y)2 symmetry are studied self-consistently employing ne wly derived Ginzburg-Landau equations. 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 four-fold anisotropy. The magnitude of the induced s-wave component depends on the relative strength between the on-site repulsive Coulomb interaction V-s aud the d-wave pairing interaction V-d. It is shown that there is a strong correlation between the struct ure of a single vortex and the shape of the vortex lattice. For modera te values of V-s/V-d our numerical calculation indicates that the stru cture of the vortex lattice is always oblique as long as the profile o f the local magnetic field around a single vortex has a four-fold symm etry. This happens usually for temperatures well below T-c. When tempe ratures are very close to T-c or V-s/V-d >> 1, the local magnetic fiel d distribution is isotropic and the vortex lattice becomes triangular. The comparison of the present result with the measurements of the vor tex lattice structure using small angle neutron scattering on YBa2Cu3O 7 samples will be discussed.