Phase-sensitive evidence for the sign-reversal s+- symmetry of the order parameter in an iron-pnictide superconductor using Nb/Ba1-xNaxFe2As2 Josephson junctions

Abstract

Josephson current between two superconductors provides a phase sensitive tool for probing their pairing symmetries. Here we fabricate and study experimentally high-quality Josephson junctions between a conventional s-wave superconductor Nb and a multi-band iron-pnictide Ba${}_{1-x}$Na${}_x$Fe${}_2$As${}_2$. Junctions exhibit a large enough critical current density to preclude the d-wave symmetry of the order parameter in the pnictide. However, the $I_c{R}_n$ product is very small $\simeq 3\mu$V, which is not consistent with the sign-preserving $s_{++}$ symmetry either. We argue that the small $I_c{R}_n$ value along with its unusual temperature dependence provide evidence for the $s_{\pm }$ symmetry of the order parameter in Ba${}_{1-x}$Na${}_x$Fe${}_2$As${}_2$. We conclude that it is the phase sensitivity of our junctions that leads to an almost complete (bellow a sub-percent) cancellation of opposite supercurrents from the sign-reversal $s_{\pm }$ bands in the pnictide.

6 pages, 2 figures. Note that there is a Supplementary information accompanying this paper

References in corpus (15)

• Evidence for an electron nematic phase transition in underdoped iron pnictide superconductors
• The Structural Phase Transition in FeSe (Fe1+dSe)
• Nematic and meta-nematic transitions in the iron pnictides
• Orbital-driven nematicity in FeSe
• Emergence of the nematic electronic state in FeSe
• Reconstruction of Band Structure Induced by Electronic Nematicity in an FeSe Superconductor
• Two-dimensional resonant magnetic excitation in BaFe1.84Co0.16As2
• (pi,pi)-electronic order in iron arsenide superconductors
• Momentum-resolved superconducting gap in the bulk of Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ from combined ARPES and $\mu$SR measurements
• Disorder-induced topological change of the superconducting gap structure in iron pnictides
• Theory of heterotic SIS Josephson junctions between single- and multi-gap superconductors
• A comprehensive scenario of the single crystal growth and doping dependence of resistivity and anisotropic upper critical fields in (Ba${}_{1-x}$K${}_x$)Fe${}_2$As${}_2$ ($0.22\le x\le 1$)
• Relation between the one-particle spectral function and dynamic spin susceptibility in superconducting Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8-\delta }$
• Phase diagram of Josephson junction between s and s+- superconductors in dirty limit
• Josephson effect and Andreev reflection in Ba(1-x)NaxFe2As2 (x=0.25 and 0.35) point contacts

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• Frustration driven Josephson phase dynamics
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