Effect of the on-site Coulomb repulsion on superconductivity in the boson-fermion model

TL;DR

This paper investigates how on-site Coulomb repulsion affects superconductivity in the boson-fermion model, focusing on anisotropic pairing and analyzing weak and strong repulsion limits.

Contribution

It provides a detailed analysis of Coulomb repulsion effects on superconductivity within the boson-fermion model, including potential crossover regimes.

Findings

Coulomb repulsion suppresses superconductivity depending on its strength.

Weak and strong repulsion regimes exhibit different impacts on the order parameter.

Possible crossover behavior between the two regimes is discussed.

Abstract

We study the influence of the repulsive Coulomb interactions on thermodynamic properties of the boson fermion model with an anisotropic (d-wave, and extended s-wave) order parameter. Superconductivity is induced in this model from the anisotropic charge exchange interaction between the conduction band fermions (electrons or holes) and the immobile hard-core bosons (the localized electron pairs). The on-site Coulomb repulsion competes with this pairing interaction and hence is expected to have a detrimental influence on superconductivity. We analyze this effect in some detail considering the two opposite limits of: the weak and strong repulsion. A possible crossover between both these regimes is also discussed.