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=1.65K 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, 117mJ K-2mol-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 (gamma_0/gamma ~ 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.
@article{arxiv.1903.02410,
title = {Unconventional Superconductivity in Heavy Fermion UTe2},
author = {Dai Aoki and Ai Nakamura and Fuminori Honda and DeXin Li and Yoshiya Homma and Yusei Shimizu and Yoshiki J. Sato and Georg Knebel and Jean-Pascal Brison and Alexandre Pourret and Daniel Braithwaite and Gerard Lapertot and Qun Niu and Michal Valiska and Hisatomo Harima and Jacques Flouquet},
journal= {arXiv preprint arXiv:1903.02410},
year = {2019}
}
Comments
5 pages, 8 figures, accepted for publication in J. Phys. Soc. Jpn