Nanoscale Interlayer Defects in Iron Arsenides

TL;DR

This study uses local microscopy to identify nanoscale interlayer defects in iron-arsenide superconductors, revealing how these defects might influence superconductivity by allowing Cooper pairs to percolate around disorder.

Contribution

The paper provides the first direct evidence of nanoscale interlayer defects in BaFe2As2 superconductors and discusses their potential impact on high-temperature superconductivity.

Findings

Interlayer defects are present along the c-axis in BaFe2As2.

Ordered atomic arrangements are observed within the ab-plane.

Interlayer defects may enable percolative superconducting pathways.

Abstract

Using a local real-space microscopy probe, we discover evidence of nanoscale interlayer defects along the c-crystallographic direction in BaFe2As2 (122) based iron-arsenide superconductors. We find ordered 122 atomic arrangements within the ab-plane, and within regions of ~10 to 20 nm size perpendicular to this plane. While the FeAs substructure is very rigid, Ba ions are relatively weakly bound and can be displaced from the 122, forming stacking faults resulting in the physical separation of the 122 between adjacent ordered domains. The evidence for interlayer defects between the FeAs superconducting planes gives perspective on the minimal connection between interlayer chemical disorder and high-temperature superconductivity. In particular, the Cooper pairs may be finding a way around such localized interlayer defects through a percolative path of the ordered layered 122 lattice that may not affect Tc.