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

Josephson junctions were fabricated in epitaxial films of cobalt-doped $BaFe2As2$ on [001]-tilt $(La,Sr)(Al,Ta)O3$ bicrystal substrates. $10-μm$-wide microbridges spanning a 30°-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.