Controllable suppression of the unconventional superconductivity in bulk and thin-film Sr_2RuO_4 via high-energy electron irradiation

In bulk Sr_2RuO_4, the strong sensitivity of the superconducting transition temperature T_c to nonmagnetic impurities provides robust evidence for a superconducting order parameter that changes sign around the Fermi surface. In superconducting epitaxial thin-film Sr_2RuO_4, the relationship between T_c and the residual resistivity ρ_0, which in bulk samples is taken to be a proxy for the low-temperature elastic scattering rate, is far less clear. Using high-energy electron irradiation to controllably introduce point disorder into bulk single-crystal and thin-film Sr_2RuO_4, we show that T_c is suppressed in both systems at nearly identical rates. This suggests that part of ρ_0 in films comes from defects that do not contribute to superconducting pairbreaking, and establishes a quantitative link between the superconductivity of bulk and thin-film samples.