Survival of the d-wave superconducting state near the edge of antiferromagnetism in the cuprate phase diagram

TL;DR

This study investigates the robustness of the d-wave superconducting state in cuprates near the antiferromagnetic boundary, revealing its persistence at very low doping levels without interference from other phases.

Contribution

It demonstrates that the d-wave superconducting state survives at low doping levels in cuprates, with superfluid density decreasing smoothly as Tc drops, without signs of competing phases.

Findings

D-wave superconductivity persists at very low doping levels.

Superfluid density declines smoothly with decreasing Tc.

No evidence of competing ordered phases affecting nodal quasiparticles.

Abstract

In the cuprate superconductor $YBa_2Cu_3O_{6+x}$, hole doping in the $CuO_2$ layers is controlled by both oxygen content and the degree of oxygen-ordering. At the composition $\rm YBa_2Cu_3O_{6.35}$, the ordering can occur at room temperature, thereby tuning the hole doping so that the superconducting critical temperature gradually rises from zero to 20 K. Here we exploit this to study the c-axis penetration depth as a function of temperature and doping. The temperature dependence shows the d-wave superconductor surviving to very low doping, with no sign of another ordered phase interfering with the nodal quasiparticles. The only apparent doping dependence is a smooth decline of superfluid density as Tc decreases.