Superfluid anisotropy in YBCO: Evidence for pair tunneling superconductivity

TL;DR

This paper investigates the superfluid anisotropy in YBCO superconductors, providing evidence that pair tunneling, rather than single-electron proximity effects, explains the observed superfluid tensor components.

Contribution

It demonstrates that pair tunneling models better explain experimental superfluid anisotropy in YBCO than conventional proximity effect models.

Findings

Proximity effect models are incompatible with experimental data.

Pair tunneling explains superfluid tensor components effectively.

Evidence supports pair tunneling as a key mechanism in YBCO superconductivity.

Abstract

Proximity effect and pair tunneling models are applied as alternative scenarios to explain the recently measured $ab$-plane and $c$-axis components of the superfluid tensor in Copper-Oxide superconductors which contain chains, such as $YBa_2Cu_3O_{6.95}$. It is argued that conventional proximity effect models, which couple chains and planes via single electron tunneling only, are incompatible with the experimental observations. On the other hand several surprising features of the experimental data are readily explained by the presence of a microscopic pair tunneling process.