Superconducting spin reorientation in spin-triplet multiple superconducting phases of UTe

Kinjo, Katsuki*; Fujibayashi, Hiroki*; Matsumura, Hiroki*; Hori, Fumiya*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; et al.

Science Advances (Internet), 9(30), p.2736_1 - 2736_6, 2023/07

https://doi.org/10.1126/sciadv.adg2736

Large reduction in the -axis knight shift on UTe with = 2.1 K

Matsumura, Hiroki*; Fujibayashi, Hiroki*; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; Shimizu, Yusei*; et al.

Journal of the Physical Society of Japan, 92(6), p.063701_1 - 063701_5, 2023/05

https://doi.org/10.7566/JPSJ.92.063701

Change of superconducting character in UTe induced by magnetic field

Kinjo, Katsuki*; Fujibayashi, Hiroki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; Shimizu, Yusei*; Homma, Yoshiya*; et al.

Physical Review B, 107(6), p.L060502_1 - L060502_5, 2023/02

https://doi.org/10.1103/PhysRevB.107.L060502

Slow electronic dynamics in the paramagnetic state of UTe

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Haga, Yoshinori; Tokiwa, Yoshifumi; Opletal, P.; Fujibayashi, Hiroki*; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; et al.

Journal of the Physical Society of Japan, 91(2), p.023707_1 - 023707_5, 2022/02

https://doi.org/10.7566/JPSJ.91.023707

Te NMR experiments in field () applied along the easy magnetization axis (the -axis) revealed slow electronic dynamics developing in the paramagnetic state of UTe. The observed slow fluctuations are concerned with a successive growth of long-range electronic correlations below 3040 K, where the spin susceptibility along the hard magnetization axis (the -axis) shows a broad maximum. The experiments also imply that tiny amounts of disorder or defects locally disturb the long-range electronic correlations and develop an inhomogeneous electronic state at low temperatures, leading to a low temperature upturn observed in the bulk-susceptibility in . We suggest that UTe would be located on the paramagnetic side near an electronic phase boundary, where either the magnetic or Fermi-surface instability would be the origin of the characteristic fluctuations.

Anisotropic response of spin susceptibility in the superconducting state of UTe probed with Te-NMR measurement

Nakamine, Genki*; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; Shimizu, Yusei*; Homma, Yoshiya*; et al.

Physical Review B, 103(10), p.L100503_1 - L100503_5, 2021/03

https://doi.org/10.1103/PhysRevB.103.L100503

Te-NMR study on a single crystal of heavy fermion superconductor UTe

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Hattori, Taisuke; Higa, Nonoka; Nakamine, Genki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Nakamura, Ai*; Shimizu, Yusei*; et al.

Journal of the Physical Society of Japan, 88(7), p.073701_1 - 073701_4, 2019/07

https://doi.org/10.7566/JPSJ.88.073701

We report Te-NMR studies on a newly discovered heavy fermion superconductor UTe. Using a single crystal, we have measured the Te-NMR Knight shift and spin-lattice relaxation rate for fields along the three orthorhombic crystal axes. The data confirm a moderate Ising anisotropy for both the static () and dynamical susceptibilities () in the paramagnetic state above about 20 K. Around 20 K, however, we have observed a sudden loss of NMR spin-echo signal due to sudden enhancement of the NMR spin-spin relaxation rate , when the field is applied along the easy axis of magnetization (= axis). This behavior suggests the development of longitudinal magnetic fluctuations along the axis at very low frequencies below 20 K.

NMR study of magnetic spin fluctuations in UTe

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Hattori, Taisuke; Higa, Nonoka*; Nakamine, Genki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Nakamura, Ai*; Shimizu, Yusei*; et al.

no journal, , 

Recently, Ran et al. reported evidence for superconductivity in the uranium-based heavy fermion material UTe, exhibiting the rather high transition temperature of 1.6 K. The ground state of UTe is paramagnetic, not ferromagnetic. However, the compound still exhibits a very large and anisotropic upper critical field H, exceeding the Pauli limit along the three principal axes, similar to the ferromagnetic superconductors, UCoGe and URhGe. Field-induced metamagnetic transition and re-entrant superconducting behaviour have been reported under strong magnetic fields around 35 T, when a magnetic field was applied along the orthorhombic hard-magnetization b-axis. In this study, we have performed Te-NMR measurements on a newly discovered heavy fermion superconductor UTe. Our NMR data confirm a moderate Ising anisotropy for both the static (K) and dynamical susceptibilities (1/) in the paramagnetic state above about 20 K.

Restriction on hidden order parameter from local symmetry at Ru site under uni-axial stress in URuSi

Kambe, Shinsaku; Sakai, Hironori; Haga, Yoshinori; Tokunaga, Yo; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Harima, Hisatomo*

no journal, , 

In this study, the local symmetry of Ru site is determined in the hidden order state under uni-axial stress along the [100] and [110] directions [4], by means of precise Ru-NQR measurements. These measurements again support the 4-fold symmetry at Ru site in the hidden order state without uni-axial stress. Furthermore, certain cases can be excluded from the previously proposed possible ones.

Slow dynamics of electrons in the paramagnetic state of UTe

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Haga, Yoshinori; Tokiwa, Yoshifumi; Opletal, P.; Fujibayashi, Hiroki*; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; et al.

no journal, , 

Ru-NQR in URuSi under uniaxial stress, 2

Kambe, Shinsaku; Haga, Yoshinori; Sakai, Hironori; Tokunaga, Yo; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Harima, Hisatomo*

no journal, , 

Consider the hidden order of URuSi. Recent studies have shown that the electronic state symmetry of hidden ordered states is restricted to a few space groups. However, since they have the same high symmetry, their distinction remains difficult. Therefore, it is necessary to see how external fields such as uniaxial pressure lower the symmetry of hidden ordered states. In this study, we discuss the Ru-NQR when the uniaxial pressure is applied to the [100] and [110] directions to form orthorhombic crystals.