Bicrystalline Grain Boundary and Hybrid SNS Junctions Based on Ba-122 Thin Films

To investigate the properties of iron-based superconductors, we examined different kinds of Josephson junctions using Co-doped Ba-122 thin films. Based on bicrystalline SrTiO₃ substrates, we prepared grain boundary (GB) junctions, which showed clear Josephson effects. We present electrical measurements at varying temperatures and magnetic fields. Furthermore, we prepared hybrid junctions using a thin-film technique. Confined by a Ba-122 base electrode (S) and a PbIn counter electrode (S^´), two different geometries of hybrid junctions are formed, i.e., a planar SNS´ junction with a gold barrier (N) in between and an edge-type junction with an interface-engineered barrier. All three kinds of junctions showed asymmetric resistively shunted junction-like behavior with ICRN products of 20.2 μV (GB junctions), 18.4 μV (planar SNS´ junctions), and 12.3 μV (edge-type junctions), respectively. An excess current could be observed at all junctions.