Band- and momentum-dependent electron dynamics in superconducting Ba(Fe_1−xCo_x)₂As₂ as seen via electronic Raman scattering

We present details of carrier properties in high quality Ba(Fe_1−xCo_x)₂As₂ single crystals obtained from electronic Raman scattering. The experiments indicate a strong band and momentum anisotropy of the electron dynamics above and below the superconducting transition, highlighting the importance of complex band-dependent interactions. The presence of low-energy spectral weight deep in the superconducting state suggests a gap with accidental nodes, which may be lifted by doping and/or impurity scattering. When combined with other measurements, our observation of band- and momentum-dependent carrier dynamics indicate that the iron arsenides may have several competing superconducting ground states.