Revealing the intrinsic properties of the heavy-fermion superconductor UBe₁₃

Even though UBe₁₃ was one of the first reported heavy-fermion superconductors, it continues to receive a considerable amount of attention due to its unconventional ground state [1 - 3]. While single crystals of UBe₁₃, grown out of Al flux, have been available early on [1], it was recently shown that their physical properties are highly affected by the Al incorporation into the lattice [4]. Even though the amount of Al atoms in the UBe₁₃ structure is rather small (< 1 - 2 at. %), it leads to dramatic changes in the physical properties. Our work provides a novel way in which polycrystalline samples of UBe₁₃ can be studied. These samples, which are inherently free of Al inclusions, provide a comprehensive examination of the inherent crystallographic defects both at the atomic- and the micro-scale. We show that these defects have a rather strong influence on the critical temperature T_c, the Sommerfeld coefficient γ, and the size of the specific heat anomaly.

[1] H. R. Ott et al., Phys. Rev. Lett. 50, 1595 (1983).
[2] G.R. Stewart, J. Low. Temp. Phys. 195, 1 (2019).
[3] Y. Shimizu et al., Phys. Rev. Lett. 122, 067001 (2019).
[4] A. Amon et al., Sci. Rep. 8, 10654 (2018).