NMR evidence for full-gap spin-triplet superconducting state in UBe

南 晶子*; 松野 治貴*; 森田 恭平*; 松木 麟太朗*; 小手川 恒*; 播磨 尚朝*; 芳賀 芳範; 山本 悦嗣; 大貫 惇睦*; 藤 秀樹*

Journal of the Physical Society of Japan, 95(7), p.074711_1 - 074711_11, 2026/07

https://doi.org/10.7566/JPSJ.95.074711

We performed Be-NMR measurements on UBe to probe its superconducting state. The Knight shift behavior indicates spin-triplet pairing with anisotropic spin susceptibility reduction below , providing strong evidence for a triplet state. The data support a multiband, fully gapped model, and symmetry analysis suggests an order parameter, consistent with a fully gapped spin-triplet topological superconductor.

Anisotropic spin fluctuations in the triangular Kondo lattice compound CePtAlGe probed by site-selective Al NMR

酒井 宏典; Shin, S.*; 神戸 振作; 徳永 陽; 播磨 尚朝*; Pomjakushina, E.*; Park, T.*

Physical Review B, 112(23), p.235102_1 - 235102_9, 2025/12

https://doi.org/10.1103/bd5f-n2yg

We report site-selective Al nuclear magnetic resonance (NMR) measurements on the Kondo-lattice compound CePtAlGe, in which Ce ions form triangular layers. By combining the measured nuclear quadrupole parameters with calculated electric field gradients, we unambiguously assign the two inequivalent Al sites and determine distinct hyperfine coupling constants dominated by Ruderman-Kittel-Kasuya-Yosida (RKKY)-type transferred fields. Spin-lattice relaxation reveals pronounced anisotropic spin fluctuations, and comparison of the two sites constrains their momentum-space structure. At low magnetic fields, is strongly enhanced on cooling toward the Nel temperature, evidencing the growth of in-plane antiferromagnetic correlations in the paramagnetic state.

Hidden order state under uni-axial stress in URuSi

神戸 振作; 石飛 尊之; 播磨 尚朝*

Journal of the Physical Society of Japan, 94(10), p.104703_1 - 104703_5, 2025/10

https://doi.org/10.7566/JPSJ.94.104703

[100]方向および[110]方向に沿った一軸応力下におけるURuSiの隠れた秩序状態の研究である。一軸応力下で誘起される空間群と秩序パラメータは、実験事実と群論的考察に基づいて推定される。一軸応力下での測定を用いて隠れた秩序の秩序パラメータを同定する手法を提案する。

First observation of the de Haas-van Alphen effect and Fermi surfaces in the unconventional superconductor UTe

青木 大*; 酒井 宏典; Opletal, P.; 常盤 欣文; 石塚 淳*; 柳瀬 陽一*; 播磨 尚朝*; 仲村 愛*; Li, D.*; 本間 佳哉*; et al.

Journal of the Physical Society of Japan, 91(8), p.083704_1 - 083704_5, 2022/08

https://doi.org/10.7566/JPSJ.91.083704

de Haas-van Alphen oscillation was successfully observed in an unconventional superconductor UTe using high-quality single crystals. From this observation, Fermi surfaces of this compound were determined to be cylinders elongated along the c-direction, in consistent with theoretical expectation. However, the extremely large cyclotron effective masses ranging 32 to 57 m, in consistent with the electronic specific heat, far exceed calculated values.

Observation of longitudinal magnetic fluctuations at a first-order ferromagnetic quantum phase transition in UGe

野間 雄一郎*; 小手川 恒*; 久保 徹郎*; 藤 秀樹*; 播磨 尚朝*; 芳賀 芳範; 山本 悦嗣; 大貫 惇睦*; 伊藤 公平*; 仲村 愛*; et al.

Journal of the Physical Society of Japan, 90(7), p.073707_1 - 073707_5, 2021/07

https://doi.org/10.7566/JPSJ.90.073707

Ferromagnetic fluctuation relevant to the pressure-induced superconductivity in UGe is investigated by means of NMR spectroscopy. Longitudinal magnetic fluctuations were observed in the spin-echo decay rate near the ferromagnetic critical point where superconductivity takes place. This result strongly suggests that superconductivity in ferromagnets is universally mediated by anisotropic magnetic fluctuations.

Quasi-one-dimensional magnetic interactions and conduction electrons in EuCu and EuAu with the characteristic hexagonal structure

松田 進弥*; 太田 譲二*; 仲井間 憲李*; 伊覇 航*; 郷地 順*; 上床 美也*; 中島 美帆*; 天児 寧*; 本多 史憲*; 青木 大*; et al.

Philosophical Magazine, 100(10), p.1244 - 1257, 2020/04

https://doi.org/10.1080/14786435.2019.1708498

Single crystal samples of EuCu and EuAu have been successfully prepared. Using those samples, magnetic and electronic anisotropy has been clarified. Magnetic moment in the ferromagnetic state points to the hexagonal -axis for both compounds. Electronic anisotropy was found in both electrical resistivity and Fermi surface topology. These anisotropic characteristics are accounted for by the unique hexagonal structure.

Single crystal growth and unique electronic states of cubic chiral EuPtSi and related compounds

大貫 惇睦*; 垣花 将司*; 伊覇 航*; 仲井間 憲李*; 青木 大*; 仲村 愛*; 本多 史憲*; 中島 美帆*; 天児 寧*; 郷地 順*; et al.

JPS Conference Proceedings (Internet), 29, p.012001_1 - 012001_9, 2020/02

https://doi.org/10.7566/JPSCP.29.012001

EuPtSi with the cubic chiral structure exhibits a skyrmion phase under magnetic field. We succeeded in growing high-quality single crystals by the Bridgman method. Fermi surface splitting reflecting the noncentrosymmetric structure was successfully observed experimentally.

Odd-parity electronic multipolar ordering in URuSi; Conclusions from Si and Ru NMR measurements

神戸 振作; 徳永 陽; 酒井 宏典; 服部 泰佑; 比嘉 野乃花; 松田 達磨*; 芳賀 芳範; Walstedt, R. E.*; 播磨 尚朝*

Physical Review B, 97(23), p.235142_1 - 235142_10, 2018/06

AA2018-0180.pdf:1.09MB

https://doi.org/10.1103/PhysRevB.97.235142

We report Si and Ru NMR measurements on high-quality, single-crystal URuSi samples with a residual resistivity ratio RRR70. Our results show that the Si and Ru sites exhibit 4-fold electronic symmetry around the -axis in the hidden-order state. A previously observed 2-fold contribution of Si NMR linewidth is concluded to be due to extrinsic magnetic centers. Since the U and Si sites are aligned along the -axis, we conclude further that the electronic state shows 4-fold symmetry around the U site below the hidden-order transition. From this observed local symmetry, possible space groups for the hidden-order state are or , based on group theoretical considerations. Since the order vector is considered to be , the hidden-order state is then found to be with rank 5 odd-parity, i.e. electric dotriacontapolar order.

Superconducting and Fermi surface properties of single crystal ZrCo

照屋 淳志*; 垣花 将司*; 竹内 徹也*; 青木 大*; 本多 史憲*; 仲村 愛*; 芳賀 芳範; 松林 和幸*; 上床 美也*; 播磨 尚朝*; et al.

Journal of the Physical Society of Japan, 85(3), p.034706_1 - 034706_10, 2016/03

https://doi.org/10.7566/JPSJ.85.034706

Superconducting characteristics and Fermi surfaces of ZrCo are experimentally studied on a single crystal sample grown by Bridgman technique. Thermodynamic quantities in the superconducting state such as specific heat and magnetization show deviation from a single-gap the BCS model and can be attributed on the band structure with the dominant contribution of Zr-4 and Co-3 components.

Characteristic fermi surface properties of VGa, CoGa, TiGa, ZrGa, and ZrAl with different tetragonal structures

照屋 淳志*; 竹田 政貴*; 仲村 愛*; 播磨 尚朝*; 芳賀 芳範; 内間 清春*; 辺土 正人*; 仲間 隆男*; 大貫 惇睦*

Journal of the Physical Society of Japan, 84(5), p.054703_1 - 054703_15, 2015/05

https://doi.org/10.7566/JPSJ.84.054703

A series of metallic compounds with the tetragonal symmetry are investigated to reveal the relationship between the structural dimensionality and the electronic structure. By combining the de Haas-van Alphen experiments and band structure calculations, a flat one-dimensional Fermi surface is revealed in VGa which is characterized by a chain like arrangement of atoms. On the other hand, CoGa with the nearly cubic symmetry has pyramidal Fermi surfaces with flat {111} planes, similar to NiGa with the ideal cubic structure.