A. Bill et al., ELECTRONIC INHOMOGENEITIES, ELECTRON-LATTICE AND PAIRING INTERACTIONSIN HIGH-T-C SUPERCONDUCTORS, Zeitschrift fur Physik. B, Condensed matter, 104(4), 1997, pp. 753-757
The presence of electronic inhomogeneities strongly reduces the screen
ing of the electron-ion interaction in high-temperature superconductor
s. This implies the existence of an non-totally screened long-range co
ntribution to the electron-lattice coupling and opens an additional ch
annel for the formation of copper pairs. We calculate the superconduct
ing order parameter taking into account a) the long-range and the shor
t-range parts of the electron-lattice interaction and b) the Coulomb r
epulsion between charge-carriers. We show that whereas the long-range
electron-lattice coupling determines the anisotropy of the order param
eter, the Coulomb repulsion and the short-range interactions determine
its symmetry. Thus, different high-T-c superconductors may have s- or
d-wave symmetry, depending on the relative strength of the interactio
ns involved in the pairing.