Orientation of point nodes and nonunitary triplet pairing tuned by the easy-axis magnetization in UTe2

Shunichiro Kittaka, Yusei Shimizu, Toshiro Sakakibara, Ai Nakamura, Dexin Li, Yoshiya Homma, Fuminori Honda, Dai Aoki, Kazushige MacHida

Research output: Contribution to journalArticlepeer-review

Abstract

The gap structure of a novel uranium-based superconductor UTe2, situated in the vicinity of ferromagnetic quantum criticality, has been investigated via specific-heat C(T,H,ω) measurements in various field orientations. Its angular ω(φ,θ) variation shows a characteristic shoulder anomaly with a local minimum in Hâ1a at moderate fields rotated within the ab and ac planes. Based on theoretical calculations, these features can be attributed to the presence of point nodes in the superconducting gap along the a direction. Under the field orientation along the easy-magnetization a axis, an unusual temperature dependence of the upper critical field at low fields together with a convex downward curvature in C(H) were observed. These anomalous behaviors can be explained on the basis of a nonunitary triplet state model with equal-spin pairing whose Tc is tuned by the magnetization along the a axis. From these results, the gap symmetry of UTe2 is most likely described by a vector order parameter of d(k)=(b+ic)(kb+ikc).

Original languageEnglish
Article number032014
JournalPhysical Review Research
Volume2
Issue number3
DOIs
Publication statusPublished - 2020 Jul

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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