Josephson junction in cobalt-doped BaFe2As2 epitaxial thin films on (La, Sr)(Al, Ta)O3 bicrystal substrates

TL;DR

This study demonstrates Josephson junction behavior in cobalt-doped BaFe2As2 epitaxial films on bicrystal substrates, highlighting the weak-link properties of grain boundaries and their potential for superconducting device applications.

Contribution

The paper reports the fabrication and characterization of Josephson junctions in iron-based superconductor films on bicrystal substrates, revealing Josephson effects across grain boundaries.

Findings

BGB bridges show RSJ-like current-voltage characteristics up to 17 K.

Critical current is significantly suppressed by magnetic fields.

BGB bridges have critical current densities 20 times lower than non-BGB bridges.

Abstract

Josephson junctions were fabricated in epitaxial films of cobalt-doped BaFe2As2 on [001]-tilt (La,Sr)(Al,Ta)O3 bicrystal substrates. 10m-wide microbridges spanning a 30-degrees-tilted bicrystal grain boundary (BGB bridge) exhibited resistively-shunted-junction (RSJ)-like current-voltage characteristics up to 17 K, and the critical current was suppressed remarkably by a magnetic field. Microbridges without a BGB did not show the RSJ-like behavior, and their critical current densities were 20 times larger than those of BGB bridges, confirming BGB bridges display a Josephson effect originating from weakly-linked BGB.