PHYSICAL PARAMETERS IN COPPER-OXIDE SUPERCONDUCTORS

Physical parameters in the so-called t-t'-J-J' model are determined for the hole-doped copper oxide superconductor, (La, Sr)2CuO4, by using the cluster model approach. We find that in the superconductor both freedoms of spin and charge, which are represented by J and t, respectively, should be taken into account on an equal basis. The dependence of Jon two factors is examined in the cluster model; one is the magnitude of 2p-3d hybridization and the other is the charge transfer energy between Cu-3d and O-2pσ orbitals in the CuO2 plane. The calculated values of J for various compounds with T-, T*- and T'-phases are compared with the experimental results. Finally, a role of apical oxygen in the Cu-oxides is examined by calculating the electronic state as a function of the energy level of the apical oxygen. © 1990, The Physical Society of Japan. All rights reserved.