Josephson junctions between a FeAs-based superconductor with antiphase s-wave pairing and a conventional s-wave superconductor are studied. The translational invariance in a planar junction between a single crystal pnictide and an aluminum metal greatly enhances the relative weight of electron pockets in the pnictide to the critical current. In a wide doping region of the pnictide, a planar and a point contact junctions have opposite phases, which can be used to design a tri-junction ring with π phase to probe the antiphase pairing.
@article{arxiv.0906.0169,
title = {$\pi$-junction to probe antiphase s-wave pairing in iron pnictide superconductors},
author = {Wei-Qiang Chen and Fengjie Ma and Zhong-Yi Lu and Fu-Chun Zhang},
journal= {arXiv preprint arXiv:0906.0169},
year = {2009}
}