Isotropic superconducting gaps with enhanced pairing on electron Fermi surfaces in FeTe0.55Se0.45

TL;DR

This study uses angle-resolved photoemission spectroscopy to reveal isotropic superconducting gaps in FeTe0.55Se0.45, supporting local antiferromagnetic exchange interactions as the pairing mechanism in this iron-based superconductor.

Contribution

It provides direct momentum-resolved evidence of isotropic gaps and fits them with a strong coupling model, clarifying the pairing origin in FeTe0.55Se0.45.

Findings

Isotropic superconducting gaps on all Fermi surfaces

Gaps fit by a single strong coupling gap function

Supports local antiferromagnetic exchange as pairing mechanism

Abstract

The momentum distribution of the energy gap opening at the Fermi level of superconductors is a direct fingerprint of the pairing mechanism. While the phase diagram of the iron-based superconductors promotes antiferromagnetic fluctuations as a natural candidate for electron pairing, the precise origin of the interaction is highly debated. We used angle-resolved photoemission spectroscopy to reveal directly the momentum distribution of the superconducting gap in FeTe1-xSex, which has the simplest structure of all iron-based superconductors. We found isotropic superconducting gaps on all Fermi surfaces whose sizes can be fitted by a single gap function derived from a strong coupling approach, strongly suggesting local antiferromagnetic exchange interactions as the pairing origin.