p-Wave Superconductivity in Iron-based Superconductors

TL;DR

This paper provides evidence that many iron-based superconductors, including NdFeAs(O,F) and FeSe, exhibit p-wave pairing, challenging the conventional understanding of their pairing symmetry.

Contribution

The study offers the first convincing evidence of bulk p-wave superconductivity in NdFeAs(O,F) and suggests that most iron-based superconductors are p-wave, based on comprehensive physical parameter analysis.

Findings

NdFeAs(O,F) is a bulk p-wave superconductor.

Single atomic layer FeSe also shows p-wave pairing.

Most iron-based superconductors are likely p-wave superconductors.

Abstract

The possibility of p-wave pairing in superconductors has been proposed more than five decades ago, but has not yet been convincingly demonstrated. One difficulty is that some p-wave states are thermodynamically indistinguishable from s-wave, while others are very similar to d-wave states. Here we studied the self-field critical current of NdFeAs(O,F) thin films in order to extract absolute values of the London penetration depth, the superconducting energy gap, and the relative jump in specific heat at the superconducting transition temperature, and find that all the deduced physical parameters strongly indicate that NdFeAs(O,F) is a bulk p-wave superconductor. Further investigation revealed that single atomic layer FeSe also shows p-wave pairing. In an attempt to generalize these findings, we re-examined the whole inventory of superfluid density measurements in iron-based superconductors show quite generally that most of the iron-based superconductors are p-wave superconductors.