Phase diagram of the one-dimensional extended attractive Hubbard model forlarge nearest-neighbor repulsion

We consider the extended Hubbard model with attractive on-site interaction U and nearest-neighbor repulsions V. We construct an effective Hamiltonian H-eff for hopping t << V and arbitrary U < 0. Retaining the most important terms, H-eff can be mapped onto two XXZ models, solved by the Bethe ansatz. The quantum phase diagram shows two Luttinger liquid phases and a region o f phase separation between them. For density n < 0.422 and U < -4, singlet superconducting correlations dominate at large distances. For some paramete rs, the results. are in qualitative agreement with experiments in Ba1-xKxBi O3.