Quasiparticle interference in antiferromagnetic parent compounds of Fe-based superconductors

TL;DR

This paper reconciles conflicting experimental observations in Fe-based superconductors by showing that Fermi surface calculations explain both the observed quasiparticle interference asymmetry and the near isotropic resistivity.

Contribution

It demonstrates that ab initio Fermi surface calculations can unify seemingly contradictory experimental results in antiferromagnetic Fe-based superconductors.

Findings

Fermi surface calculations match quasiparticle interference data

Resistivity anisotropy is consistent with similar Fermi velocities

C2 asymmetry does not necessarily imply electronic nematicity

Abstract

Recently reported quasiparticle interference imaging in underdoped Ca(Fe{1-x}Co{x})_2As{2} shows pronounced C{2} asymmetry that is interpreted as an indication of an electronic nematic phase with a unidirectional electron band, dispersive predominantly along the $b$-axis of this orthorhombic material. On the other hand, even more recent transport measurements on untwinned samples show near isotropy of the resistivity in the $ab$ plane, with slightly larger conductivity along a (and not b). We show that in fact both sets of data are consistent with the calculated ab initio Fermi surfaces, which has a decisively broken C_{4}, and yet similar Fermi velocity in both directions. This reconciles completely the apparent contradiction between the conclusions of the STM and the transport experiments.