Electron irradiation of iron-based superconductors

The premise of $\mbox{s}_{\pm } $ superconductivity in the multiband iron-based superconductors, with a sign-changing order parameter between the electron-like and hole-like Fermi-surface sheets, has raised the question of the effect of atomic-scale point-like disorder on superconductivity in these materials. In this contribution, we compare the effect of the controlled introduction of point-like defects in different 122-type iron-based superconductors by 2.5 MeV electron irradiation at 20 K. Preliminary data reveal that the effect point-like defects on the critical temperature of isovalently doped materials vastly outweighs that on the charge-doped compounds. The weak collective contribution to $J_{c}$ in Co-doped 122 compounds is found to clearly increase. Moreover this contribution appears after irradiation of the P-doped compound in which it was previously absent.