Comparison of response of superconductivity to impurity concentration in UBe₁₃ and LuBe₁₃

Journal Article · 09 March 2022 · Physica. B, Condensed Matter

DOI: https://doi.org/10.1016/j.physb.2022.413792 · OSTI ID:1977547

Kim, J. S. ^[1]; Stewart, G. R.  ^[2]

---

1. University of Florida, Gainesville, FL (United States); OSTI
2. University of Florida, Gainesville, FL (United States)

Uhlirova et al. reported superconductivity in LuBe₁₃ and assigned it tentatively to be BCS-type, with specific heat measurements down to 0.45 K showing the partial onset of a bulk transition. In order to check LuBe13 for unconventional behavior, as well as to further characterize the unconventional superconductivity in UBe₁₃, we have prepared and characterized down to 0.40 K three arc-melted samples each of MBe₁₃, M = Lu, U, using three different purities (99.999%, 99.96%, and 99.8%) of Be but with the same high purity M (Lu or U) for all three. The measurements down to 0.40 K allow the detection of the maximum in the specific heat in all three LuBe₁₃ samples. The resulting superconducting properties strongly depend on impurity level in UBe₁₃ (40% decrease in ΔC/T_c, 15% decrease in T_c^mid) while the three LuBe₁₃ samples exhibit significantly smaller changes (10% and 5% respectively) with purity. The comparison of properties at the first two levels of purity (99.999% vs 99.96%) is even more disparate: 12% decrease in T_c^mid in UBe₁₃ vs no change in LuBe₁₃. Furthermore, these results are consistent with previous results that argue for unconventional superconductivity in UBe₁₃ and are consistent with Uhlirova et al.‘s assignment of LuBe₁₃ as a conventional, BCS superconductor. More generally, this example of comparing superconducting properties vs-controlled gradations in impurity levels with two compositionally and structurally “matched” superconducting compounds (one conventional and one of to-be-determined coupling behavior) offers a new method for determining unconventional behavior.

• Research Organization: University of Florida, Gainesville, FL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0020385
• OSTI ID: 1977547
• Alternate ID(s): OSTI ID: 1856050
• Journal Information: Physica. B, Condensed Matter, Journal Name: Physica. B, Condensed Matter Journal Issue: C Vol. 635; ISSN 0921-4526
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English