Unconventional superconductivity in heavy fermion Ute2

Dai Aoki, Ai Nakamura, Fuminori Honda, De Xin Li, Yoshiya Homma, Yusei Shimizu, Yoshiki J. Sato, Georg Knebel, Jean Pascal Brison, Alexandre Pourret, Daniel Braithwaite, Gerard Lapertot, Qun Niu, Michal Vališka, Hisatomo Harima, Jacques Flouquet

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55 Citations (Scopus)

Abstract

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 H ∥ b-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.

Original languageEnglish
Article number043702-
Journaljournal of the physical society of japan
Volume88
Issue number4
DOIs
Publication statusPublished - 2019
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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