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Journal Articles Journal of the Physical Society of Japan Year : 2019

Unconventional superconductivity in heavy fermion UTe$_2$

Dai Aoki
Ai Nakamura
• Function : Author
Fuminori Honda
Dexin Li
• Function : Author
Yoshiya Homma
Yusei Shimizu
Yoshiki Sato
Georg Knebel
Jean-Pascal Brison
Alexandre Pourret
Gérard Lapertot
• Function : Author
• PersonId : 834505
Qun Niu
• Function : Author
Michal Vališka
Hisatomo Harima
• Function : Author
Jacques Flouquet
• Function : Author
• PersonId : 854566

Abstract

We grew single crystals of the recently discovered heavy fermion superconductor UTe$_2$, and measured the resistivity, specific heat and magnetoresistance. Superconductivity (SC) was clearly detected at $T_{sc}$ = 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 $T_{sc}$ 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 $T_{sc}$ 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 $H_{c2}$ along the three principal axes favors spin-triplet SC. For $H$ ∥ $b$-axis, our experiments do not reproduce the huge upturn of $H_{c2}$ reported previously. This discrepancy may reflect that $H_{c2}$ is very sensitive to the sample quality. A new perspective in UTe$_2$ is the proximity of a Kondo semiconducting phase predicted by the LDA band structure calculations.

Dates and versions

hal-02145738 , version 1 (03-06-2019)

Identifiers

• HAL Id : hal-02145738 , version 1
• DOI :

Cite

Dai Aoki, Ai Nakamura, Fuminori Honda, Dexin Li, Yoshiya Homma, et al.. Unconventional superconductivity in heavy fermion UTe$_2$. Journal of the Physical Society of Japan, 2019, 88 (4), pp.043702. ⟨10.7566/JPSJ.88.043702⟩. ⟨hal-02145738⟩

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