概要

　Spin-triplet superconductivity is presently very much sought after in the field of quantum engineering for its potential topological excitations. However, this state, albeit quite rare in nature, does exist in a few bulk compounds, mainly uranium-based systems like UPt₃ [1], URhGe [2] or UTe₂ [3].
Due to the additional spin degrees of freedom, spin-triplet superconductors may present several competing superconducting phases differing by their symmetries, and emerging under specific ranges of temperature, magnetic field or pressure[1]. They can also withstand much larger magnetic field values than spin-singlet superconductors, and often exhibit unusual field-induced behaviors [3,4].
We discuss results on UTe₂ obtained mainly by thermodynamic measurements under high magnetic fields and under pressure [5,6,7], and compare them to the case of other known spin-triplet superconductors. It reveals how the different superconducting phases and the anomalous field behavior of this system may arise from different mechanisms, and remain presently a very exciting puzzle.

References
[1] Joynt and Taillefer, Rev. Mod. Phys. 2002, 74, 235-294
[2] Aoki et al., Nature 2001, 413, 613-616
[3] Ran et al., Science,2019, 365, 684-687
[4] Levy et al. Nature Physics,2007, 3, 460-463
[5] Rosuel et al., Phys. Rev. X 2023, 13, 011022
[6] Helm et al., Nature Communications,2024, 15, 37
[7] Vasina et al., ArXiv 2024, 2410.17733

問合先：井澤 公一
izawa@mp.es.osaka-u.ac.jp