High temperature superconductivity from realistic long-range Coulomb and Fr\"ohlich interactions

TL;DR

This paper presents a realistic model combining Coulomb and electron-phonon interactions to explain high-temperature superconductivity, demonstrating a phase transition with Tc exceeding 100K and supporting the polaron-bipolaron theory.

Contribution

It introduces a comprehensive model incorporating Coulomb, Fr"ohlich, and Hubbard interactions without assumptions on their relative strengths, providing a microscopic basis for high-Tc superconductivity.

Findings

Phase transition to superconductivity with Tc > 100K

Role of Hubbard U as a key parameter in BEC/BCS crossover

Supports polaron-bipolaron theory as a microscopic foundation

Abstract

In the last years ample experimental evidence has shown that charge carriers in high-temperature superconductors are strongly correlated but also coupled with lattice vibrations (phonons), signaling that the true origin of high-Tc superconductivity can only be found in a proper combination of Coulomb and electron-phonon interactions. On this basis, we propose and study a model for high-Tc superconductivity, which accounts for realistic Coulomb repulsion, strong electron-phonon (Fr\"ohlich) interaction and residual on-site (Hubbard \tilde{U}) correlations without any ad-hoc assumptions on their relative strength and interaction range. In the framework of this model, which exhibits a phase transition to a superconducting state with a critical temperature Tc well in excess of 100K, we emphasize the role of \tilde{U} as the driving parameter for a BEC/BCS crossover. Our model lays a microscopic foundation for the polaron-bipolaron theory of superconductivity. We argue that the high-Tc phenomenon originates in competing Coulomb and Fr\"ohlich interactions beyond the conventional BCS description.