From microscopic description to statistical mechanics of Cu-O chain fragments in the high-Tc superconductors REBa2Cu3O6+x

Haugerud, H.
Department of Physics, University of Oslo,
Blindern 03156 Oslo,

Uimin, G.
Institut für Theoretische Physik, Universität zu Köln,
D-50937 Köln, Germany
Departement de Recherche Fondamentale sur la Matiere Condensee,
SPSMS/MDN, CENG, 17, rue des Martyrs,
F-38054 Grenoble Cedex 9, France

Selke, W.
Institut für Theoretische Physik, Technische Hochschule Aachen,
D-52056 Aachen, Germany


The oxygen deficient CuOx planes of the high-Tc superconductors REBa2Cu3O6+x (RE denotes a rare-earth atom or yttrium) are studied. Starting from the Emery model for the Cu-O chain fragments, an extended ASYNNNI model is proposed to describe the statistical mechanics of the CuOx planes. The model is analysed by using Monte Carlo techniques, computing especially the charge transfer to the CuO2 planes regulating the high-Tc superconductivity, and the concentration of differently coordinated Cu ions. Results are compared to experimental data for various RE cases.