Singular Band Behavior of the Extended Emery Model for the Superconducting Cuprates

Mean field slave-boson approximation is performed on the extended Emery model for the CuO2 conducting plane. The model is parameterized by Cu–O charge transfer energy Δ pd , copper–oxygen overlap t0, oxygen–oxygen overlap t', and Coulomb interaction U on the copper site taken as infinite. Special emphasis is placed on the role of t′ in the renormalization trends of the effective band parameters Δ pf and t, replacing Δ pd and t0, at small doping δ. It is shown that small, negative t′ expands the range of stability of the metallic phase, changing, in the second order of the perturbation theory, the nature of the metal–insulator transition point. In the nonperturbative limit, t′ modifies strongly the renormalization of Δ pf , making it saturate at the value of 4∣t′∣. Finite doping suppresses the insulating state approximately symmetrically with respect to its sign. The regime Δ pf ≈ 4∣t′∣ fits very well the ARPES spectra of Y123, Bi2212, and LSCO and also explans, in the latter case, the evolution of the FS with doping accompanied by the spectral weight-transfer from the oxygen to the resonant band.