Observation of the Josephson effect in Pb/(Ba,K)Fe2As2 single crystal junctions

TL;DR

This study demonstrates Josephson coupling in Pb/(Ba,K)Fe2As2 junctions, indicating an s-wave superconducting order parameter in iron pnictide superconductors through experimental fabrication and measurement of junctions.

Contribution

First observation of Josephson effect in (Ba,K)Fe2As2 single crystal junctions using Pb, revealing s-wave pairing symmetry in iron pnictides.

Findings

Josephson effect observed in both planar and point contact geometries.

Microwave steps and magnetic field suppression consistent with small junctions.

ICRN products up to 0.3 mV at 4.2 K.

Abstract

We have fabricated c-axis Josephson junctions on single crystals of (Ba,K)Fe2As2 by using Pb as the counter electrode in two geometries, planar and point contact. Junctions in both geometries show resistively shunted junction I-V curves below the Tc of the counter electrode. Microwave induced steps were observed in the I-V curves, and the critical currents are suppressed with an in-plane magnetic field in a manner consistent with the small junction limit. ICRN products of up to 0.3 mV have been observed in these junctions at 4.2 K. The observation of Josephson coupling along the c-axis between (Ba,K)Fe2As2 and a conventional superconductor suggests the existence of a s-wave superconducting order parameter in this class of iron pnictide superconductors.