Relevance and irrelevance of three effective Hamiltonians for high-temperature superconductors with CuO2 planes

Abstract

Photoemission spectra of high-temperature cuprate-oxide superconductors are consistent with band calculations; Cu 3d levels are shallower than O 2p levels by about 1 eV. When effects of shallow and broad 3d and 2p levels are taken into account, the superexchange interaction is substantially reduced but still it is as strong as J≃−0.1 eV within the three-band periodic Anderson model called the d−p model that takes into account Cu 3dx2−y2, O 2px, and O 2py orbits. The d−p model whose parameters are consistent with photoemission spectra is a relevant model for the cuprate oxides; the coupling constant for dx2−y2-wave superconductivity, which is approximately proportional to the density of states of quasiparticles and the superexchange interaction, is large enough to explain observed critical temperatures as high as Tc=50−100 K. The t−J model with t≃−0.21 eV and J≃−0.1 eV is also a relevant model for the cuprate oxides. When the reduction of the superexchange interaction is taken into account, on the other hand, Tc’s of the Hubbard model whose parameters are consistent with the two relevant models are substantially lower than their Tc’s.

Source-reported materials — not catalogue approval

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