Bulk electronic structure of optimally doped Ba(Fe$_{1-x}$Co$_{x}$)$_2$As$_2$

TL;DR

This study uses high-resolution bulk Compton scattering to map the Fermi surface of an optimally-doped iron-based superconductor, confirming theoretical predictions and providing insights into its three-dimensional electronic structure and potential superconductivity mechanisms.

Contribution

It provides the first experimental bulk Fermi surface measurements of Ba(Fe$_{1-x}$Co$_{x}$)$_2$As$_2$, validating first-principles calculations and analyzing Fermi-surface nesting effects.

Findings

Fermi surface features match first-principles calculations.

Strong three-dimensionality observed in one Fermi surface sheet.

Fermi-surface nesting persists despite three-dimensionality.

Abstract

We report high-resolution, bulk Compton scattering measurements unveiling the Fermi surface of an optimally-doped iron-arsenide superconductor, Ba(Fe$_{0.93}$Co$_{0.07}$)$_2$As$_2$. Our measurements are in agreement with first-principles calculations of the electronic structure, revealing both the $X$-centered electron pockets and the $\Gamma$-centered hole pockets. Moreover, our data are consistent with the strong three-dimensionality of one of these sheets that has been predicted by electronic structure calculations at the local-density-approximation-minimum As position. Complementary calculations of the noninteracting susceptibility, $\chi_0({\bf q}, \omega)$, suggest that the broad peak that develops due to interband Fermi-surface nesting, and which has motivated several theories of superconductivity in this class of material, survives the measured three dimensionality of the Fermi surface in this family.