Mesoscopic Phase Separation in Anisotropic Superconductors

TL;DR

This paper analyzes how mesoscopic phase separation influences anisotropic superconductors, revealing conditions for stability, effects on critical temperature, and implications for different pairing symmetries, aligning with experimental observations in cuprates.

Contribution

It provides a theoretical framework for understanding the role of phase separation in enhancing or suppressing superconductivity in anisotropic materials.

Findings

Phase separation is stable only with repulsive Coulomb interactions.

Superconductivity can emerge in heterophase samples even if absent in pure phases.

Critical temperature is higher in mixed pairing symmetry states.

Abstract

General properties of anisotropic superconductors with mesoscopic phase separation are analysed. The main conclusions are as follows: Mesoscopic phase separation can be thermodynamically stable only in the presence of repulsive Coulomb interactions. Phase separation enables the appearance of superconductivity in a heterophase sample even if it were impossible in pure-phase matter. Phase separation is crucial for the occurrence of superconductivity in bad conductors. Critical temperature for a mixture of pairing symmetries is higher than the critical temperature related to any pure gap-wave symmetry of this mixture. In bad conductors, the critical temperature as a function of the superconductivity fraction has a bell shape. Phase separation makes the single-particle energy dispersion softer. For planar structures phase separation suppresses d-wave superconductivity and enhances s-wave superconductivity. These features are in agreement with experiments for cuprates.