THE VIBRONIC APPROACH TO HIGH-TC SUPERCONDUCTIVITY

Recent experimental and theoretical studies have been stressing the relationship between the pairing mechanism and the motion of apical oxygens in high-T(c) materials. Earlier we had proposed a similar model of vibronically coupled charge transfer from planes to chains producing asymmetrically distorted Cu-O polyhedra to move and pair as small polarons. Numerical data for LaSCO proved to be in optimistic agreement with the experimental T(c). This model is now revisited both as a theoretical background and as a backing up of experimental evidence. Its particular relationship with the inferred ferroelectricity of high-T(c) materials will be analyzed.