Phase separation and valence instabilities in cuprate superconductors: Effective one-band-model approach

M. E. Simón; A. A. Aligia

doi:10.1103/PhysRevB.53.15327

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Phase separation and valence instabilities in cuprate superconductors: Effective one-band-model approach

M. E. Simón, A. A. Aligia

DOI 10.1103/PhysRevB.53.15327 · Physical Review B

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Abstract

We study the Cu-O valence instability (VI) and the related phase separation (PS) driven by Cu-O nearest-neighbor repulsion Upd, using an effective extended one-band Hubbard (Heff) obtained from the extended three-band Hubbard, through an appropriate low-energy reduction. Heff is solved by exact diagonalization of a square cluster with 10 unit cells and also within a slave-boson mean-field theory. Its parameters depend on doping for Upd≠0 and on-site O repulsion Up≠0. The results using both techniques coincide in that there is neither VI nor PS for doping values levels x<0.5 if Upd≳2 eV. The PS region begins for Upd≳2 at large doping x≳0.6 and increases with increasing Upd. The PS also increases with increasing on-site Cu repulsion Ud. © 1996 The American Physical Society.