Superconductivity, Charge Orderings and Phase Separations in Systems with Local Electron Pairing

TL;DR

This paper investigates models of superconductors with short coherence lengths, revealing complex phase diagrams with multiple phase-separated states and the influence of long-range interactions on these phases.

Contribution

It introduces a comprehensive analysis of phase separations and competition between superconductivity and charge orderings in two effective models, extending previous work with new phase states and interaction effects.

Findings

Identification of at least seven distinct states including three phase-separated types.

Demonstration of the impact of long-range interactions on phase stability.

Generalization of previous models to include more complex phase behaviors.

Abstract

We study two effective models developed for description of superconductors with short-coherence length: (i) the extended Hubbard model with on-site attraction and intersite repulsion, (ii) the model of hard-core charged bosons on a lattice. The analysis is concentrated on the problem of phase separations and competition between superconductivity (SS) and charge-density-wave (CDW) orderings. The phase diagrams of the systems are shown to consist of at least seven different states, including 3 types of phase separated (PS) states: CDW-SS (PS1), CDW-normal (PS2) and the state of electron droplets (PS3). By taking into account the PS states and the effects of longer-range density-density interactions (beyond nearest neighbours) our work substantially generalizes and modifies the conclusions of previous works concerning the models considered.