Observation of intertwined Fermi surface topology, orbital parity symmetries and electronic interactions in iron arsenide superconductors

TL;DR

This study uses advanced photoemission techniques to reveal complex Fermi surface topology, symmetry breaking, and electronic interactions in optimally doped iron arsenide superconductors, shedding light on their superconducting mechanisms.

Contribution

It provides a polarization and topology resolved analysis of the low energy band structure, uncovering unexpected symmetry breaking and intertwined Fermi surface features in Ba0.6K0.4Fe2As2.

Findings

Revealed unexpected symmetry breaking in the band structure.

Identified intertwined Fermi surface topology of hole-like bands.

Suggested spin-mediated interband interactions contribute to superconductivity.

Abstract

We present a polarization and topology resolved study of the low energy band structure in optimally doped superconducting Ba0.6K0.4Fe2As2 using angle resolved photoemission spectroscopy. Polarization-contrasted measurements allow us to identify and trace all low energy bands expected in models, revealing unexpected symmetry breaking and a surprisingly intertwined Fermi surface topology of hole-like bands near the Brillouin zone center. Band structure correlations across the Gamma-M spin fluctuation wavevector are compared with the superconducting gap anisotropy which suggest a partial scenario for spin-mediated interband instability contributing to superconductivity in the hole doped regime.