Mixing of superconducting d(x2-y2) state with s-wave states for different filling and temperature

We study the order parameter for mixed-symmetry states involving a major d( x2-y2) state and various minor s-wave states (s, s(xy), and Sx2+y2) for dif ferent filling and temperature for mixing angles 0 and pi /2. We employ a t wo-dimensional tight-binding model incorporating second-neighbor hopping fo r tetragonal and orthorhombic lattice. There is mixing for the symmetric s state both on tetragonal and orthorhombic lattice. The s(xy) state mixes wi th the d(x2-y2) state only on orthorhombic lattice. The s(x2+y2) state neve r mixes with the d(x2-y2) state. The temperature dependence of the order pa rameters is also studied. (C) 2001 Elsevier Science B.V. All rights reserve d.