Bulk electronic structure of optimally doped Ba( Fe_1-xCo _x)₂As₂

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 As₂. Our measurements are in agreement with first-principles calculations of the electronic structure, revealing both the X -centered electron pockets and the Γ -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, χ0 (q,ω), 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.