Pair breaking in iron-based superconductors

The relative ease of crystal growth combined with the range of elements available for chemical substitution, especially on the transition metal site, has allowed for numerous studies of different iron-based superconductors. There are, however, remaining questions about the pairing symmetry in this system. We present transport scattering rate data for optimally-doped single crystals from several superconducting 122 materials and discuss the relationship between superconducting transition temperature and transport scattering rate in the context of pair breaking.