Family tree of perovskite-related superconductors

TL;DR

This paper identifies an empirical relation linking the critical temperature of perovskite-related superconductors to their mean cation charge, suggesting a common superconductivity mechanism across different compounds.

Contribution

It introduces a simple empirical relation between Tc and <qc> that applies to both conventional and cuprate superconductors, proposing a unified understanding.

Findings

Tc increases exponentially as <qc> decreases.

A Ba-based cuprate with <qc> around 2 could reach Tc about 200 K.

Structural assignment for high-Tc phase is proposed.

Abstract

A simple empirical relation has been found to exist between optimum Tc and the formal mean cation charge <qc> of perovskite-related superconductors, covering both conventional superconductors and superconducting cuprates. Tc is shown to increase exponentially with decreasing <qc>. It is suggested that a Ba-based cuprate with <qc> about 2 reach a Tc around 200 K. The strong correlation may be thought of as an indication for a common mechanism of superconductivity of the whole family of compounds. In addition, the structural assignment for the 'cubic' high-Tc phase reported by Volkov (Tc = 117 K) to the orthorhombic BaCuO2.5 prototype is proposed.