Froehlich-Coulomb model of high-temperature superconductivity and charge segregation in the cuprates

TL;DR

This paper presents a Froehlich-Coulomb model for oxides, explaining high-temperature superconductivity and charge segregation in cuprates through analytical solutions of multi-polaron problems, matching key experimental features.

Contribution

It introduces a new Froehlich-Coulomb model with an analytical method to solve multi-polaron problems in complex lattices, explaining various phenomena in cuprates.

Findings

Carriers form superlight bipolarons in the superconducting phase.

The model reproduces key features of cuprates such as Tc, isotope effects, and pseudogap.

Depending on interactions, systems can be polaronic liquids, bipolarons, or charge segregated insulators.

Abstract

We introduce a generic Froehlich-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 zig-zag ladder and a perovskite layer, are studied. We find that depending on the relative strength of the Froehlich 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 Tc 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.