Origin of Gap Anisotropy in Spin Fluctuation Models of the Fe-pnictides

TL;DR

This paper investigates the origin of gap anisotropy in spin fluctuation models of Fe-pnictides, emphasizing the importance of intra- and inter-Fermi surface pair scattering and orbital makeup in understanding anisotropic s-wave states.

Contribution

It reveals that considering pair scattering within and between Fermi surface sheets and their orbital composition is essential to explain gap anisotropy in Fe-pnictides.

Findings

Large gap anisotropy in A1g s-wave state explained by intra- and inter-Fermi surface scattering.

Orbital makeup of Fermi surface states crucial for understanding anisotropy.

Simple isotropic models need to be supplemented with detailed scattering and orbital considerations.

Abstract

We discuss the large gap anisotropy found for the A1g (s-wave) state in RPA spin-fluctuation and functional renormalization group calculations and show how the simple arguments leading to isotropic sign-switched s-wave states in these systems need to be supplemented by a consideration of pair scattering within Fermi surface sheets and between the individual electron sheets as well. In addition, accounting for the orbital makeup of the states on the Fermi surface is found to be crucial.