Evolution of structural dependent superconducting properties on Re-Os-W-Mo-Ta high entropy alloys

Structural, superconducting ground state, and normal state properties on Re-Os-W-Mo-Ta high-entropy alloys (HEAs) were investigated using powder x-ray diffraction, magnetization measurements, electrical resistivity analysis, and specific heat measurements. The structural phase transformation was found to develop through compositional variations of the primary elements of HEAs, leading to the formation of phases such as bcc-type Re23Os5W33Mo34Ta5, σ-type Re31Os18W23Mo23Ta5, and α-Mn-type Re33Os34W11Mo11Ta11. These impurity-free samples, displaying a single-phase structure, exhibit bulk superconducting behavior. Low-temperature specific heat analysis indicates that the bcc-type and σ-type HEAs exhibit weakly coupled, whereas the α-Mn-type HEA exhibits strongly coupled, isotropic and fully gapped superconductivity. Moreover, the stability of bcc-type, σ-type, and α-Mn-type HEAs is significantly influenced by key factors such as valence electron count and electronegativity differences. This study presents observations of structural transformations in HEAs driven by compositional variations without the introduction of additional elements, providing significant insights into the correlation between structural changes and superconducting properties in highly disordered systems.