Superconductivity of Ta-Hf and Ta-Zr alloys: Potential alloys for use in superconducting devices

Abstract

The electronic properties relevant to the superconductivity are reported for bulk Ta-Hf and Ta-Zr body centered cubic alloys, in large part to determine whether their properties are suitable for potential use in superconducting qbits. The body centered cubic unit cell sizes increase with increasing alloying. The results of magnetic susceptibility, electrical resistivity and heat capacity characterization are reported. While elemental Ta is a type I superconductor, the alloys are type II strong coupling superconductors. Although decreasing the electron count per atom is expected to increase the density of electronic states at the Fermi level and thus the superconducting transition temperature (Tc) in these systems, we find that this is not sufficient to explain the significant increases in the superconducting Tc's observed.

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• Superconductivity with high upper critical field in Ta-Hf Alloys
• Discovery of the Type-II Superconductor Ta${}_4$Rh${}_2$C${}_{1-\delta }$ with a High Upper Critical Field
• Einstein and Debye temperatures, electron-phonon coupling constant and a probable mechanism for ambient-pressure room-temperature superconductivity in intercalated graphite
• Insight into high-entropy effect in body-centered cubic superconducting alloys