Abstract

We consider superconductivity in the presence of impurities in a
two-band model suited for the description of iron-based superconductors.
We analyze the effect of interband scattering processes on
superconductivity, allowing for orbital, i.e., non-spin-magnetic
time-reversal-symmetry-breaking impurities. Pair-breaking in such
systems is described by a nontrivial phase in an interband-scattering
matrix element. We find that the transition temperature of conventional
superconductors can be suppressed due to interband scattering, whereas
unconventional superconductors may be unaffected. As an example, we
consider impurities associated with orbital density waves that are of
interest for iron-based superconductors.