Monotonic Doping-Dependence in the Anisotropy of the Drude Weight and Scattering Rate of Detwinned Ba(Fe1−x Co x )2As2 Established from the Optical Conductivity

Abstract

We investigate the anisotropic metallic response in the optical conductivity of fully detwinned Ba(Fe1−x Co x )2As2 in their underdoped regime. We estimate the Drude weight and the scattering rates of the itinerant charge carriers across the structural (at T s ) and magnetic (at T N ) phase transition. Our findings support a monotonic doping dependence of the anisotropy of both parameters determining the transport properties, opposite to the non-monotonic anisotropy of the dc resistivity between the crystallographic axes. The capability of optical methods to address a broad energy interval extending far away from the Fermi level allows emphasizing the prominent role of the electronic structure rather than the impurity scattering when establishing a direct connection with the long-range ferro-orbital and antiferromagnetic orders.