$\pi$-junction to probe antiphase s-wave pairing in iron pnictide superconductors

TL;DR

This paper proposes using a $$-junction between an iron pnictide superconductor with antiphase s-wave pairing and a conventional s-wave superconductor to detect the pairing symmetry through phase measurements.

Contribution

It introduces a novel junction design that enhances electron pocket contributions and demonstrates how phase differences can reveal antiphase pairing in iron pnictides.

Findings

Planar junctions increase electron pocket contribution to critical current.

Opposite phase behavior observed in different junction types across doping levels.

Proposed tri-junction ring can serve as a phase-sensitive probe for pairing symmetry.

Abstract

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 $\pi$ phase to probe the antiphase pairing.