Superconductivity in zigzag CuO chains

TL;DR

This paper proposes a theoretical model for superconductivity in zigzag CuO chains, supported by DMRG and bosonization studies, explaining recent experimental findings in Pr-based cuprates.

Contribution

It introduces a new phase, C$_1$S$_{3/2}$, for zigzag CuO chains with unique spin and charge properties, supported by microscopic modeling and numerical analysis.

Findings

Identification of the C$_1$S$_{3/2}$ phase with specific gap properties.

Evidence from DMRG and bosonization supporting the proposed phase.

Explanation of superconductivity in zigzag CuO chains despite insulating CuO planes.

Abstract

Superconductivity has recently been discovered in Pr$_{2}$Ba$_{4}$Cu$_{7}$O$_{15-\delta}$ with a maximum $T_c$ of about 15K. Since the CuO planes in this material are believed to be insulating, it has been proposed that the superconductivity occurs in the double (or zigzag) CuO chain layer. On phenomenological grounds, we propose a theoretical interpretation of the experimental results in terms of a new phase for the zigzag chain, labelled by C$_1$S$_{3/2}$. This phase has a gap for some of the relative spin and charge modes but no total spin gap, and can have a divergent superconducting susceptibility for repulsive interactions. A microscopic model for the zigzag CuO chain is proposed, and on the basis of density matrix renormalization group (DMRG) and bosonization studies of this model, we adduce evidence that supports our proposal.