The effect of disorder on electronic Raman scattering in the superconducting state of iron pnictides

Electronic Raman scattering measures a polarization-dependent scattering intensity which can provide information about the location of nodes in the energy gap of an unconventional superconductor as well as its overall symmetry. In this paper, we calculate the Raman intensity in the presence of disorder for several models of the iron pnictide superconducting state. We include, for completeness, $d$-wave and isotropic $s_\pm$ responses in addition to more realistic extended $s_\pm$ superconducting gaps. The effect of disorder is modeled using a self-consistent $T$-matrix approximation, and is studied in the limits of isotropic and intraband-only scattering. We show how recent experiments on Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ may be consistent with "node lifting" by intraband disorder.