Rare earth ion size dependence of the T<inf>c</inf>of the "RE-123" HTSC within the (d + s)-wave description of their superconducting state

Abstract

The dependence of the Tc's on the radius of the rare earth ions in the rare earth "123" high temperature superconductors (HTSC) is explained within the framework of a (d + s)-wave model of superconductivity. The appearance of a s-wave symmetry component in the order parameter of a spin fluctuation mediated d-wave superconductor is taken to be due to the orthorhombic distortion which occurs in these HTSC. It is assumed that the structural (orthorhombic) distortion induces a corresponding anisotropy in the pairing interaction, resulting in a nonseparable anisotropic interaction. It is shown that the Tc's are affected by the orthorhombic distortion which in turn is observed to depend on the size of the RE ions. © 1998 Elsevier Science B.V.