### Abstract

The exact ground-state energy E0 is calculated for a one-dimensional copper-oxide model defined on a ring of finite length L, threaded by an external flux . It includes on-site and nearest-neighbor intersite Coulomb repulsion V, as well as a nonzero bare oxide gap 0 between the orbitals in the unit cell. The correlation exponent K of the corresponding low-energy Hamiltonian shows that singlet (extended s-wave) superconductivity has the most rapidly diverging susceptibility as T0 (K>1). This superconducting phase is located close to a phase-separation instability of the model, indicated by K. Longer range of the Coulomb interaction tends to frustrate phase separation, enhances the range of V for which K>1, and slightly broadens the regime of V where 1<K<.

Original language | English |
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Pages (from-to) | 553-560 |

Number of pages | 8 |

Journal | Physical Review B |

Volume | 51 |

Issue number | 1 |

DOIs | |

Publication status | Published - Jan 1 1995 |

### ASJC Scopus subject areas

- Condensed Matter Physics

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## Cite this

*Physical Review B*,

*51*(1), 553-560. https://doi.org/10.1103/PhysRevB.51.553