Angle-resolved photoemission evidence of s-wave superconducting gap in KxFe2-ySe2 superconductor

TL;DR

This study provides angle-resolved photoemission evidence supporting s-wave pairing symmetry in KxFe2-ySe2 superconductors by demonstrating an isotropic superconducting gap on the small electron Fermi pocket.

Contribution

It offers direct experimental evidence of s-wave pairing symmetry in KxFe2-ySe2, clarifying the nature of its superconducting gap.

Findings

Isotropic superconducting gap observed on the small electron Fermi pocket.

Supports s-wave pairing symmetry over d-wave in KxFe2-ySe2.

Provides insight into pairing mechanisms in iron-based superconductors.

Abstract

Although nodeless superconducting gap has been observed on the large Fermi pockets around the zone corner in KxFe2-ySe2, whether its pairing symmetry is s-wave or nodeless d-wave is still under intense debate. Here we report an isotropic superconducting gap distribution on the small electron Fermi pocket around the Z point in KxFe2-ySe2, which favors the s-wave pairing symmetry.