Crossover behavior for complex order parameter in high-T-c superconductors

A number of recent experiments have suggested the presence of either real o r complex components in the gap symmetry of high-T-c superconductors (HTSC) . Ln this paper we introduce a novel approach to study the competition of s uch complex order parameter mixtures by varying the position of the two-bod y attractive potential in a two-dimensional extended Hubbard Hamiltonian. W e show that this procedure explains a number of experimental results and on the theoretical side, it may be related with certain HTSC microscopic mode ls like the spin fluctuation theory. Following current trends we concentrat e on the study of d(x2-y2) order parameter with a component of the type d(x y) or a s-wave-like s(x2+y2) and s(xy) symmetry. We show that the position of the optimal s-component peak changes with the position parameter b while the d-component occurs always in the optimal region around hole content rh o approximate to 0.39. These studies may be useful to interpret some experi mental data and to explain why similar experiments yield different gap symm etries. (C) 1999 Elsevier Science B.V. All rights reserved.