On the Liaison Between Superconductivity and Phase Separation

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, ${\mathrm{V}}_{\mathrm{coul}}$, is increased. Due to this effect, the domain of stability of the superconducting phases that appear near phase separation at ${\mathrm{V}}_{\mathrm{coul}}=0$ 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.

11 pages, 9 postscript figures are appended