Multiple Nodeless Superconducting Gaps in (Ba0.6K0.4)Fe2As2 Superconductor from Angle-Resolved Photoemission Spectroscopy

TL;DR

This study uses angle-resolved photoemission spectroscopy to reveal multiple nodeless superconducting gaps in (Ba0.6K0.4)Fe2As2, providing detailed insights into its pairing mechanism and gap symmetry.

Contribution

It presents the first detailed measurement of multiple superconducting gaps in (Ba0.6K0.4)Fe2As2, highlighting their size, momentum dependence, and isotropy, which advances understanding of iron-based superconductor pairing.

Findings

Two hole-like Fermi surface sheets have different gaps.

Gaps are nodeless and isotropic, supporting s-wave symmetry.

Superconducting gaps persist above Tc at certain points.

Abstract

High resolution angle-resolved photoemission measurements have been carried out to study the superconducting gap in the (Ba0.6K0.4)Fe2As2 superconductor with Tc=35 K. Two hole-like Fermi surface sheets around the G(0,0) point exhibit different superconducting gaps. The inner Fermi surface sheet shows larger (10-12 meV) and slightly momentum-dependent gap while the outer one has smaller (7-8 meV) and nearly isotropic gap. The lack of gap node in both Fermi surface sheets favours s-wave superconducting gap symmetry. Superconducting gap opening is also observed at the M(pi,pi) point. The two Fermi surface spots near the M point are gapped below Tc but the gap persists above Tc. The rich and detailed superconducting gap information will provide key insights and constraints in understanding pairing mechanism in the iron-based superconductors.