We examine the nature of Josephson junction between two identical Fe-pnictides with anti-phase s-wave pairing. pi-phase shift is found if the junction barrier is thick and the two Fe-pnictides are oriented in certain directions relative to the interface. Our theory provides a possible explanation for the observed half integer flux quantum transitions in a niobium/polycrystal NdFeAsO loop, and attributes the pi-phase shift to intergrain junctions of Fe-pnictides.
@article{arxiv.1009.4756,
title = {Possible pi-phase shift at interface of two pnictides with antiphase s-wave pairing},
author = {Wei-Qiang Chen and Fu-Chun Zhang},
journal= {arXiv preprint arXiv:1009.4756},
year = {2011}
}