Scaling of the superconducting gap with orbital character in FeSe

TL;DR

This study combines experimental ARPES measurements and theoretical modeling to reveal that the superconducting gap in FeSe scales with the $d_{yz}$ orbital weight, supporting a spin-fluctuation mediated pairing mechanism.

Contribution

It demonstrates the orbital dependence of the superconducting gap in FeSe and provides a theoretical framework that matches experimental observations.

Findings

Superconducting gap follows the $d_{yz}$ orbital distribution.

Theoretical model agrees with experimental gap structure.

Supports spin-fluctuation mediated superconductivity in FeSe.

Abstract

We use high-resolution angle-resolved photoemission spectroscopy to map the three-dimensional momentum dependence of the superconducting gap in FeSe. We find that on both the hole and electron Fermi surfaces, the magnitude of the gap follows the distribution of $d_{yz}$ orbital weight. Furthermore, we theoretically determine the momentum dependence of the superconducting gap by solving the linearized gap equation using a tight binding model which quantitatively describes both the experimental band dispersions and orbital characters. By considering a Fermi surface only including one electron pocket, as observed spectroscopically, we obtain excellent agreement with the experimental gap structure. Our finding of a scaling between the superconducting gap and the $d_{yz}$ orbital weight supports the interpretation of superconductivity mediated by spin-fluctuations in FeSe.