Influence of self-irradiation on the magnitude of the superfluid density in probed by muon spin rotation

We have performed muon spin rotation ( μ SR ) measurements in the radioactive Pu-based superconductor PuCoGa 5 to study the effects of radiation damage on the superconducting properties. The same single crystals were studied 25 days (fresh) and 400 days (aged) after initial preparation. We find that the μ SR rate σ v , which is proportional to superfluid density ρ s , is steeply reduced in the aged sample compared with its reduction of T c . This result is inconsistent with conventional Abrikosov–Gor’kov pair-breaking theory, but can be explained by the local suppression of the order parameter in a strong-scattering, short-coherence-length superconductor.