Electronic structure in one-Fe Brillouin zone of iron-pnictide superconductor CsFe$_2$As$_2$

TL;DR

This study uses ARPES to demonstrate that the electronic spectral weight in CsFe$_2$As$_2$ follows the 1-Fe Brillouin zone, providing insights into the validity of theoretical models based on this zone in iron-pnictide superconductors.

Contribution

It provides experimental evidence supporting the relevance of the 1-Fe Brillouin zone in highly hole-doped iron-pnictide superconductors, challenging previous interpretations based on the 2-Fe zone.

Findings

Spectral weight distribution follows the 1-Fe BZ

Band structure differs from 1-Fe BZ theoretical models

Interlayer separation influences electronic structure

Abstract

The multiband nature of iron-pnictide superconductors is one of the keys to the understanding of their intriguing behavior. The electronic and magnetic properties heavily rely on the multiband interactions between different electron and hole pockets near the Fermi level. At the fundamental level, though many theoretical models were constructed on the basis of the so-called 1-Fe Brillouin zone (BZ) with an emphasis of the basic square lattice of iron atoms, most electronic structure measurements were interpreted in the 2-Fe BZ. Whether the 1-Fe BZ is valid in a real system is still an open question. Using angle-resolved photoemission spectroscopy (ARPES), here we show in an extremely hole-doped iron-pnictide superconductor CsFe$_2$As$_2$ that the distribution of electronic spectral weight follows the 1-Fe BZ, and that the emerging band structure bears some features qualitatively different from theoretical band structures of the 1-Fe BZ. Our analysis suggests that the interlayer separation is an important tuning factor for the physics of FeAs layers, the increase of which can reduce the coupling between Fe and As and lead to the emergence of the electronic structure in accord with the 1-Fe symmetry of the Fe square lattice. Our finding puts strong constraints on the theoretical models constructed on the basis of the 1-Fe BZ.