On the Liaison Between Superconductivity and Phase Separation

TL;DR

This paper investigates how long-range Coulomb interactions influence phase separation and superconductivity in strongly correlated electron models, revealing that charge-density-wave states become stable with increased Coulomb repulsion, but superconductivity persists over a broad parameter range.

Contribution

It demonstrates that long-range 1/r interactions stabilize charge-density-wave states and do not extend the superconducting phase region as expected, providing insights into cuprate theories.

Findings

Charge-density-wave states become stable with increased Coulomb repulsion.

Superconductivity remains stable over a wide parameter space despite phase separation suppression.

Long-range interactions do not enlarge the superconducting region as naively expected.

Abstract

Models of strongly correlated electrons that tend to phase separate are studied including a long-range 1/r repulsive interaction. It is observed that charge-density-wave states become stable as the strength of the 1/r term, ${\rm V_{coul}}$, is increased. Due to this effect, the domain of stability of the superconducting phases that appear near phase separation at ${\rm V_{coul} = 0}$ is not enlarged by a 1/r interaction as naively expected. Nevertheless, superconductivity exists in a wide region of parameter space, even if phase separation is suppressed. Our results have implications for some theories of the cuprates.