Suppression of the transition to superconductivity in crystal/glass high-entropy alloy nanocomposites

Abstract

Superconducting high entropy alloys (HEAs) may combine extraordinary mechanical properties with robust superconductivity. They are suitable model systems for the investigation of the interplay of disorder and superconductivity. Here, we report on the superconductivity in (TaNb)1-x(ZrHfTi)x thin films. Beyond the near-equimolar region, the films comprise hundreds-of-nanometer-sized crystalline grains and show robust bulk superconductivity. However, the superconducting transitions in these nanocomposites are dramatically suppressed in the near-equimolar configurations, i.e., 0.45 < x < 0.64, where elemental distributions are equivalently homogeneous. Crystal/glass high entropy alloy nanocomposite phase separation was observed for the films in the near-equimolar region, which yields a broadened two-step normal to superconducting transition. Furthermore, the diamagnetic shielding in these films is only observed far below the onset temperature of superconductivity. As these unusual superconducting transitions are observed only in the samples with the high mixing entropy, this compositional range influences the collective electronic properties in these materials.