J. Phys. Soc. Jpn. 88, 043702 (2019) [5 Pages]
LETTERS

Unconventional Superconductivity in Heavy Fermion UTe2

Anne de Visser
JPSJ News Comments 16,  08 (2019).

+ Affiliations
1IMR, Tohoku University, Oarai, Ibaraki 311-1313, Japan2University Grenoble Alpes, CEA, IRIG-PHELIQS, F-38000 Grenoble, France3Graduate School of Science, Kobe University, Kobe 657-8501, Japan

We grew single crystals of the recently discovered heavy fermion superconductor UTe2, and measured the resistivity, specific heat and magnetoresistance. Superconductivity (SC) was clearly detected at Tsc = 1.65 K as sharp drop of the resistivity in a high quality sample of RRR = 35. The specific heat shows a large jump at Tsc indicating strong coupling. The large Sommerfeld coefficient, γ = 117 mJ K−2 mol−1 extrapolated in the normal state and the temperature dependence of C/T below Tsc are the signature of unconventional SC. The discrepancy in the entropy balance at Tsc between SC and normal states points out that hidden features must occur. Surprisingly, a large residual value of the Sommerfeld coefficient seems quite robust (γ0/γ ∼ 0.5). The large upper critical field Hc2 along the three principal axes favors spin-triplet SC. For Hb-axis, our experiments do not reproduce the huge upturn of Hc2 reported previously. This discrepancy may reflect that Hc2 is very sensitive to the sample quality. A new perspective in UTe2 is the proximity of a Kondo semiconducting phase predicted by the LDA band structure calculations.

©2019 The Physical Society of Japan

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