COUPLING OF THE IONIC MOTIONS WITH THE ELECTRONIC-STRUCTURE IN THE YBA2CU3O7 HIGH T-C SUPERCONDUCTOR

Abstract

A theoretical analysis of the consequences of the experimentally measured double-well oscillation of the apical oxygen in YBa2Cu3O7 is made. The electronic structure was calculated in the frozen phonon approximation with different apical oxygen positions of a cell consisting 4-unit cells. Chemical bond changes are related to chain-planes electronic interactions and with valence fluctuations of the Cu(1) atoms of the chains. A vibronic mechanism is substantiated as a candidate for strong phonon-electron interaction. The coupling of the ionic motions with electronic structure, in turn, explains valence fluctuation, bipolaron and magnetic-like phenomena in these type of compounds.