Phase-Sensitive Evidence for the Sign-Reversal s± Symmetry of the Order Parameter in an Iron-Pnictide Superconductor Using Nb/Ba1−xNaxFe2As2 Josephson Junctions

• Josephson current provides a phase-sensitive tool for probing the pairing symmetry. Here we present an experimental study of high-quality Josephson junctions between a conventional s-wave superconductor Nb and a multiband iron-pnictide Ba1−xNaxFe2As2. Junctions exhibit a large enough critical current density to preclude the d-wave symmetry of the order parameter in the pnictide. However, the IcRn product is very small ≃3μV, which is not consistent with the sign-preserving s++ symmetry either. We argue that the small IcRn value, along with its unusual temperature dependence, provides evidence for the sign-reversal s± symmetry of the order parameter in Ba1−xNaxFe2As2. We conclude that it is the phase sensitivity of our junctions that leads to an almost complete (below a subpercent) cancellation of supercurrents from sign-reversal bands in the pnictide.

Ämnesord

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

Nyckelord

Unconventional superconductivity

Tunneling

Josephson effect

Physics

fysik

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