Unusual Fermi surface nesting in parent compounds of iron arsenic high temperature superconductors revealed by Angle Resolved Photoemission Spectroscopy

TL;DR

This study uses ARPES to reveal unique Fermi surface nesting and band hybridization in parent compounds of iron arsenic superconductors, suggesting a potential link to magnetic order and a possible failed charge density wave.

Contribution

It uncovers unusual incommensurate Fermi surface nesting and band back folding in BaFe2As2 and CaFe2As2, providing new insights into their electronic structure and magnetic properties.

Findings

Fermi surface has long parallel segments along kz

Presence of incommensurate nesting at low temperatures

Evidence of band back folding and hybridization

Abstract

We use angle resolved photoemission spectroscopy (ARPES) to study the band structure of BaFe2As2 and CaFe2As2, two of the parent compounds of the iron arsenic high temperature superconductors. We find clear evidence for band back folding and hybridization demonstrating that conduction electrons are strongly affected by the emergence of magnetic order. Our high quality data revealed that although the Fermi surface is strongly three-dimensional, it does indeed have long parallel segments along the kz direction that can lead to the emergence of magnetic order. More interestingly, we find very unusual incommensurate nesting of the Fermi surface in the a-b plane that is present only at low temperatures. We speculate that this is a signature of a failed Charge Density Wave (CDW) state that was predicted by renormalization group studies.