Field dependence of the vortex structure in d-wave and s-wave superconductors

We study the vortex structure and its field dependence within the framework of the quasiclassical Eilenberger theory to find the difference between the d_x²-y^2- and s-wave pairings. We clarify the effect of the d_x²-y^2- wave nature and the vortex lattice effect on the vortex structure of the pair potential, the internal field and the local density of states. The d_x²-y^2- wave pairing introduces a fourfold-symmetric structure around each vortex core. With increasing field, their contribution becomes significant to the whole structure of the vortex lattice state, depending on the vortex lattice’s configuration. It is reflected in the form factor of the internal field, which may be detected by small-angle neutron scattering, or the resonance line shape of muon spin resonance and NMR experiments. We also study the induced s- and d_xy^- wave components around the vortex in d_x²-y^2- wave superconductors.