Coexistence of $s$-wave superconductivity and phase separation in the half-filled extended Hubbard model with attractive interactions

TL;DR

This paper introduces a novel approach to the extended Hubbard model, revealing a new phase where s-wave superconductivity coexists with phase separation, relevant for understanding complex electronic materials.

Contribution

The study applies a multi-channel fluctuating field approach to identify a new coexistence phase in the attractive extended Hubbard model, advancing understanding of competing instabilities.

Findings

Discovery of a phase with coexisting s-wave superconductivity and phase separation.

Identification of this phase in the attractive extended Hubbard model.

Relevance to high-temperature superconductors and electronic systems.

Abstract

Understanding competing instabilities in systems with correlated fermions remains one of the holy grails of modern condensed matter physics. Among the fermionic lattice models used to this effect, the extended Hubbard model occupies a prime place due to the potential relevance of its repulsive and attractive versions for both electronic materials and artificial systems. Using the recently introduced multi-channel fluctuating field approach, we address the interplay of charge density wave, $s$-wave superconductivity, and phase separation fluctuations in the attractive extended Hubbard model. Despite of the fact that this model has been intensively studied for decades, our novel approach has allowed us to identify a novel phase that is characterised by the coexistence of $s$-wave superconductivity and phase separation. Our findings resonate with previous observations of interplaying phase separation and superconducting phases in electronic systems, most importantly in high-temperature superconductors.