Anisotropic order parameters with s- and d-wave-like symmetry and the transition temperature in high-${\mathit{T}}_{\mathit{c}}$ layered superconductors

The wave-vector dependence of superconducting order parameters and the corresponding transition temperature in three-dimensional layered metals are investigated. It includes planar anisotropic s-wave-like as well as d-wave-like pairing contributions, but for simplicity only intralayer pairing of electrons has been considered for tetragonal and orthorhombic crystal structures, relevant to high-${\mathit{T}}_{\mathit{c}}$ materials. It is shown that for the orthorhombic case order parameters are likely to have mixed symmetry, whereas in tetragonal structures it is possible to have only planar d-wave-like symmetry with a possible correction term with an additional wave-vector dependence in the direction perpendicular to the reciprocal layer plane. © 1996 The American Physical Society.