Slave Boson Description of CuO2 Planes of the High-Temperature Superconductors

Slave-boson mean-field calculation is carried out analytically for doped CuO2 conduction planes, described by the extended Emery model which is parameterized by Cu–O charge transfer energy Δpd, Cu–O hopping t0, O–O hopping t′ and Coulomb repulsion U localized on Cu site, taken as infinite. At zero doping δ, finite small t′ expands the range of stability of the covalent, conducting state, characterized by renormalized band parameters Δpf and t, on the expense of insulating t=0 state, which, however, remains stable at larger Δpd. For sufficiently large Δpd, Δpf saturates at 4|t′|. Finite doping suppresses the insulating state nearly symmetrically with respect to its sign. The regime with Δpf close to 4|t′| fits remarkably well ARPES spectra of Y123, Bi2212 and LSCO, and, in the latter case, explains the observed strong doping-dependence of the effective Cu–O hopping.