Tuning the interlayer spacing in high T_c superconductors: penetration depth and two-dimensional superfluid density

TL;DR

This study demonstrates that increasing interlayer spacing in Bi-based high T_c superconductors affects the penetration depth but not T_c, indicating the superfluid density's two-dimensional nature within layers governs superconducting properties.

Contribution

It provides experimental evidence that the superfluid density relevant to T_c is two-dimensional and unaffected by interlayer spacing modifications.

Findings

Penetration depth increases with layer separation.

T_c remains nearly constant despite interlayer spacing changes.

Superfluid density within layers is constant across systems.

Abstract

Substantial control of the interlayer spacing in Bi-based high temperature superconductors has been achieved through the intercalation of guest molecules between the superconducting layers. Measurements using implanted muons reveal that the penetration depth increases with increasing layer separation while T_c does not vary appreciably, demonstrating that the bulk superfluid density is not the determining factor controlling T_c. Our results strongly suggest that the superfluid density appearing in the Uemura scaling relation n_s/m* \propto T_c should be interpreted as the two dimensional density within the superconducting layers, which we find to be constant for each class of system investigated.