Temperature dependence of the superfluid density as a probe for multiple gaps in Ba(Fe_(0.9)Co_(0.1))_2As_2: Manifestation of three weakly interacting condensates

摘要

The knowledge about the gap size and structure is of utmost importance for a theory of the superconducting pairing mechanism. The number of superconducting gaps is an important part of the description and modeling of multiband systems such as the iron-based superconductors. Here, we present a study on the temperature dependence of the superfluid density, ρ_s(T), in Ba(Fe_(0.9)Co_(0.1))_2As_2 obtained from terahertz spectra of conductivity and dielectric permittivity of thin film samples with critical temperatures T_c ≈ 20-22 K. We demonstrate that the temperature dependence of the superfluid density, ρ_s(T), can be explained best by a model of three interacting superconducting condensates. Our results refine the standard two-band approach for Co-doped BaFe_2As_2.