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.
@article{arxiv.0812.3605,
title = {Observation of the Josephson effect in Pb/(Ba,K)Fe2As2 single crystal junctions},
author = {Xiaohang Zhang and Yoon Seok Oh and Yong Liu and Liqin Yan and Kee Hoon Kim and Richard L. Greene and Ichiro Takeuchi},
journal= {arXiv preprint arXiv:0812.3605},
year = {2009}
}