Phase Separation and the Phase Diagram in Cuprates Superconductors

TL;DR

This paper models the phase diagram of cuprate superconductors by considering disorder-induced phase separation, explaining the pseudogap and superconducting transition through inhomogeneous charge distributions and percolation.

Contribution

It introduces a novel approach combining Cahn-Hilliard and Bogoliubov-deGennes methods to explain the phase separation and inhomogeneity in cuprates.

Findings

Phase separation correlates with the pseudogap line T*

Charge inhomogeneity develops into superconductivity via percolation

Different cuprates exhibit varying degrees of charge and spin segregation

Abstract

We show that the main features of the cuprates superconductors phase diagram can be derived considering the disorder as a key property of these materials. Our basic point is that the high pseudogap line is an onset of phase separation which generates compounds made up of regions with distinct doping levels. We calculate how this continuous temperature dependent phase separation process occurs in high critical temperature superconductors (HTSC) using the Cahn-Hilliard approach, originally applied to study alloys. Since the level of phase separation varies for different cuprates, it is possible that different systems with average doping level pm exhibit different degrees of charge and spin segregation. Calculations on inhomogeneous charge distributions in form of stripes in finite clusters performed by the Bogoliubov-deGennes superconducting approach yield good agreement to the pseudogap temperature T*(pm), the onset of local pairing amplitudes with phase locked and concomitantly, how they develop at low temperatures into the superconducting phase at Tc(pm) by percolation.