Effect of Chemical Substitution on Spin-Triplet Superconductivity in UTe2

Unconventional spin-triplet superconductivity in UTe2 has recently attracted significant attention due to several remarkable features, including ultra-high and anisotropic upper critical fields exceeding the Pauli limit, a minuscule Knight shift across the superconducting transition, a reentrant superconducting phase above 40 T, and topologically nontrivial behavior with chiral in-gap surface states, pair-density-wave, and charge-density-wave orders [1-7]. However, strong sample-to-sample variations in superconducting behavior—such as the appearance of single or double superconducting transitions and variations in Tc (1.6-2.1 K) depending on preparation conditions—remain incompletely understood. Although these effects are often attributed to atomic defects, the superconducting state in UTe2 generally does not exhibit the extreme sensitivity to disorder expected for a spin-triplet superconductor. Therefore, further investigation into the role of defects in these crystals is crucial to understanding their unique superconducting properties. In this study, we examine the effect of chemical substitution at the U-site to introduce controlled disorder and explore its impact on the spin-triplet superconducting properties of UTe2.