Superconducting ground state properties on equiatomic TaNbZrTi and TaNbHfZr medium entropy alloys

We investigate the superconducting ground state properties of the equiatomic medium entropy alloys (MEAs) TaNbZrTi and TaNbHfZr using comprehensive dc magnetization and transport measurements. Bulk superconductivity is observed in both MEAs, with superconducting Tc of 8.12 K for TaNbZrTi and 7.64 K for TaNbHfZr among the highest reported for equiatomic MEAs. The collective pinning behavior in both MEAs is governed by the coexistence of point and planar defects, which serve as effective pinning centers and enhance flux-line stabilization. Low-temperature specific heat measurements reveal moderate coupled, fully gapped superconductivity in both MEAs, with characteristics that significantly exceed the predictions of conventional BCS theory. The synergistic interplay of metallic character, upper critical fields, and flux pinning nature in these MEAs positions them as a promising new platform for superconducting materials in high-field magnet applications.