Pinpointing Gap Minima in Ba(Fe$_{0.94}$Co$_{0.06})_{2}$As$_2$ \textit{via} Band Structure Calculations and Electronic Raman Scattering

TL;DR

This study combines band structure calculations and electronic Raman scattering to identify the location of gap minima in the superconductor Ba(Fe$_{0.94}$Co$_{0.06})_{2}$As$_2$, clarifying its complex gap topology.

Contribution

It introduces a method using Raman scattering geometries and density functional calculations to pinpoint gap minima locations in Fe-pnictide superconductors.

Findings

Gap minima may occur on loops over the c-axis.

Raman scattering geometries can clarify gap topology.

Density functional calculations support the gap minima location.

Abstract

A detailed knowledge of the gap structure for the Fe-pnictide superconductors is still rather rudimentary, with several conflicting reports of either nodes, deep gap minima, or fully isotropic gaps on the Fermi surface sheets, both in the $k_{x}-k_{y}$ plane and along the c-axis. In this paper we present considerations for electronic Raman scattering which can help clarify the gap structure and topology using different light scattering geometries. Using density functional calculations for the Raman vertices, it is shown that the location of the gap minima may occur on loops stretching over a portion of the c-axis in Ba(Fe$_{0.94}$Co$_{0.06})_{2}$As$_2$.