Coupling between planes and chains in YBa2Cu3O7 : a possible solution for the order parameter controversy

TL;DR

This paper proposes a model for YBa2Cu3O7 that explains contradictory experimental results on the order parameter by considering coupling between planes and chains, resulting in a mixed s- and d-wave symmetry with nodes.

Contribution

It introduces a novel coupling model between planes and chains that accounts for the order parameter symmetry and resolves experimental contradictions in YBa2Cu3O7.

Findings

Anticrossing of plane and chain bands occurs due to coupling.

Opposite signs of order parameters on planes and chains are predicted.

The model naturally explains the presence of nodes in the superconducting gap.

Abstract

We propose to explain the contradictory experimental evidence about the symmetry of the order parameter in $YBa_{2}Cu_{3}O_{7} $ by taking into account the coupling between planes and chains. This leads to an anticrossing of the plane and chain band. We include an attractive pairing interaction within the planes and a repulsive one between planes and chains, leading to opposite signs for the order parameter on planes and chains, and to nodes of the gap because of the anticrossing. Our model blends s-wave and d-wave features, and provides a natural explanation for all the contradictory experiments