Controllable suppression of the unconventional superconductivity in bulk and thin-film Sr${}_2$RuO${}_4$ via high-energy electron irradiation

Abstract

In bulk Sr${}_2$RuO${}_4$, the strong sensitivity of the superconducting transition temperature $T_{\text{c}}$ to nonmagnetic impurities provides robust evidence for a superconducting order parameter that changes sign around the Fermi surface. In superconducting epitaxial thin-film Sr${}_2$RuO${}_4$, the relationship between $T_{\text{c}}$ and the residual resistivity ${\rho }_0$, 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${}_2$RuO${}_4$, we show that $T_{\text{c}}$ is suppressed in both systems at nearly identical rates. This suggests that part of ${\rho }_0$ 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.