Effect of Artifical Disorder on Superconductivity and Charge Density Wave Ordering in (Ca, Sr)3(Rh, Ir)4Sn13 Superconductors

The evolution of the temperature-dependent resistivity with artificial disorder induced by low-temperature ($\sim$ 20 K) 2.5 MeV electron irradiation was studied in the “3-4-13” stannides, (Ca, Sr)$_3$(Rh, Ir)$_4$Sn$_{13}$ in stoichiometric compositions. This type of irradiation is known to create point defects affecting electron scattering rate without affecting the electronic band structure, and thus providing a unique tuning parameter to gently perturb the system. In these three-dimensional cubic compounds, charge density wave ordering is universally suppressed by the introduction of disorder. Matthiessen’s rule is obeyed above the transition in Sr$_3$Rh$_4$Sn$_{13}$ and Sr$_3$Ir$_4$Sn$_{13}$ , but not in high superconducting T$_c$ compounds Ca$_3$Ir$_4$Sn$_{13}$ and Ca$_3$Rh$_4$Sn$_{13}$. The superconducting transition temperature initially increases in Sr$_3$Rh$_4$Sn$_{13}$ in a way which is consistent with the competition of CDW and SC phases, but it shows rapid saturation and does not continue to rise upon further irradiation. In Sr$_3$Ir$_4$Sn$_{13}$ and Ca$_3$Ir$_4$Sn$_{13}$ the superconducting transition temperature decreases with irradiation. Surprisingly, the superconducting transition of Ca$_3$Rh$_4$Sn$_{13}$ (which does not have a long-range CDW order) also decreases, violating Anderson theorem and hence suggesting potential unconventional superconductivity in this compound.

This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences, Materials Science and Engineering Division. Ames Laboratory is operated for the U.S. DOE by Iowa State University under contract DE-AC02-07CH11358. This work is also done with the support of U.S. DOE-BES, Division of Materials Science and Engineering, Contract DE-SC0012704. The 2.5 MeV electron irradiation was performed at the “SIRIUS” facility in Ecole Polytechnique, Palaiseau, France, a part of EMIR&A French national network of accelerators under proposal number 20-5925.