1 3 M ar 2 00 2 Fröhlich - Coulomb model of high - temperature superconductivity and charge segregation in the cuprates

Fröhlich-Coulomb model of high-temperature superconductivity and charge segregation in the cuprates. Abstract. We introduce a generic Fröhlich-Coulomb model of the oxides, which also includes infinite on-site (Hubbard) repulsion, and describe a simple analytical method of solving the multi-polaron problem in complex lattice structures. Two particular lattices, a zigzag ladder and a perovskite layer, are studied. We find that depending on the relative strength of the Fröhlich and Coulomb interactions these systems are either polaronic Fermi (or Luttinger)-liquids, bipolaronic superconductors, or charge segregated insulators. In the superconducting phase the carriers are superlight mobile bipolarons. The model describes key features of the cuprates such as their T c values, the isotope effects, the normal state diamagnetism, pseudogap, and spectral functions measured in tunnelling and photoemission. We argue that a low Fermi energy and strong coupling of carriers with high-frequency phonons is the cause of high critical temperatures in novel superconductors.