Angle-resolved photoemission study of the role of nesting and orbital orderings in the antiferromagnetic phase of BaFe2As2

TL;DR

This study uses angle-resolved photoemission to analyze the electronic structure and orbital changes in BaFe2As2 across its magnetic transition, revealing the importance of nesting and orbital orderings in its antiferromagnetic phase.

Contribution

It provides a detailed experimental analysis of the electronic structure, nesting, and orbital evolution in BaFe2As2, highlighting the role of imperfect nesting and orbital redistribution in its magnetic phase transition.

Findings

Imperfect nesting explains gap formation and metallic droplets in AFM phase.

Band shifts and splittings occur at the transition, with splittings being surface sensitive.

Orbital occupations, especially in dxz/dyz, are significantly redistributed at the transition.

Abstract

We present a detailed comparison of the electronic structure of BaFe2As2 in its paramagnetic and antiferromagnetic (AFM) phases, through angle-resolved photoemission studies. Using different experimental geometries, we resolve the full elliptic shape of the electron pockets, including parts of dxy symmetry along its major axis that are usually missing. This allows us to define precisely how the hole and electron pockets are nested and how the different orbitals evolve at the transition. We conclude that the imperfect nesting between hole and electron pockets explains rather well the formation of gaps and residual metallic droplets in the AFM phase, provided the relative parity of the different bands is taken into account. Beyond this nesting picture, we observe shifts and splittings of numerous bands at the transition. We show that the splittings are surface sensitive and probably not a reliable signature of the magnetic order. On the other hand, the shifts indicate a significant redistribution of the orbital occupations at the transition, especially within the dxz/dyz system, which we discuss.