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Superconducting spin reorientation in spin-triplet multiple superconducting phases of UTe$$_2$$

金城 克樹*; 藤林 裕己*; 松村 拓輝*; 堀 文哉*; 北川 俊作*; 石田 憲二*; 徳永 陽; 酒井 宏典; 神戸 振作; 仲村 愛*; et al.

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

Superconducting (SC) state has spin and orbital degrees of freedom, and spin-triplet superconductivity shows multiple SC phases because of the presence of these degrees of freedom. However, the observation of spin-direction rotation occurring inside the SC state (SC spin rotation) has hardly been reported. Uranium ditelluride, a recently found topological superconductor, exhibits various SC phases under pressure: SC state at ambient pressure (SC1), high-temperature SC state above 0.5 gigapascal (SC2), and low-temperature SC state above 0.5 gigapascal (SC3). We performed nuclear magnetic resonance (NMR) and ac susceptibility measurements on a single-crystal uranium ditelluride. The b axis spin susceptibility remains unchanged in SC2, unlike in SC1, and decreases below the SC2-SC3 transition with spin modulation. These unique properties in SC3 arise from the coexistence of two SC order parameters. Our NMR results confirm spin-triplet superconductivity with SC spin parallel to b axis in SC2 and unveil the remaining of spin degrees of freedom in SC uranium ditelluride.


HTTR広領域中性子検出器の開発; 熱サイクル負荷に対する耐熱性能の向上

小澤 太教; 菅沼 拓朗; 本間 史隆; 東村 圭祐*; 鵜飼 隆由*; 齋藤 賢司

JAEA-Technology 2023-007, 24 Pages, 2023/06




Low-temperature magnetic fluctuations investigated by $$^{125}$$Te-NMR on the uranium-based superconductor UTe$$_2$$

藤林 裕己*; 金城 克樹*; 仲嶺 元輝*; 北川 俊作*; 石田 憲二*; 徳永 陽; 酒井 宏典; 神戸 振作; 仲村 愛*; 清水 悠晴*; et al.

Journal of the Physical Society of Japan, 92(5), p.053702_1 - 053702_5, 2023/05

 被引用回数:0 パーセンタイル:0(Physics, Multidisciplinary)

To investigate the static and dynamic magnetic properties on the uranium-based superconductor UTe$$_2$$, we measured the NMR Knight shift $$K$$ and the nuclear spin lattice relaxation rate 1/$$T_1$$ in $$H//a$$ by $$^{125}$$Te-NMR on a $$^{125}$$Te-enriched single-crystal sample. 1/$$T_1$$$$T$$ in $$H//a$$ is much smaller than 1/$$T_1$$$$T$$ in $$H //b$$ and c, and magnetic fluctuations along each axis are derived from the 1/$$T_1$$$$T$$ measured in $$H$$ parallel to all three crystalline axes. The magnetic fluctuations are almost identical at two Te sites and isotropic at high temperatures, but become anisotropic below 40 K, where heavy-fermion state is formed.


Large reduction in the $$a$$-axis knight shift on UTe$$_2$$ with $$T_c$$ = 2.1 K

松村 拓輝*; 藤林 裕己*; 金城 克樹*; 北川 俊作*; 石田 憲二*; 徳永 陽; 酒井 宏典; 神戸 振作; 仲村 愛*; 清水 悠晴*; et al.

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

Spin susceptibility in the superconducting (SC) state was measured in the higher-quality sample of uranium-based superconductor UTe$$_2$$ by using Knight-shift measurements for a magnetic field $$H$$ along all three crystalline axes. In the higher-quality sample, the SC transition temperature $$T_c$$ is about 2.1 K, and the residual electronic term in the specific heat is almost zero. The NMR linewidth becomes narrower and is almost half of that in the previous sample with $$T_csim$$1.6 K when $$H//a$$ and $$c$$. Although the Knight-shift behavior was not so different from the previous results for $$H//b$$, and $$c$$, a large reduction in Knight shift along the $$a$$ axis was observed, in contrast with the previous $$a$$-axis Knight shift result. We discuss the origin of the difference between the previous and present results, and the possible SC state derived from the present results.


Change of superconducting character in UTe$$_{2}$$ induced by magnetic field

金城 克樹*; 藤林 裕己*; 北川 俊作*; 石田 憲二*; 徳永 陽; 酒井 宏典; 神戸 振作; 仲村 愛*; 清水 悠晴*; 本間 佳哉*; et al.

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

 被引用回数:2 パーセンタイル:93.34(Materials Science, Multidisciplinary)

UTe$$_2$$ is a recently discovered spin-triplet superconductor. One of the characteristic features of UTe$$_2$$ is a magnetic field ($$H$$)-boosted superconductivity above 16 T when H is applied exactly parallel to the $$b$$ axis. To date, this superconducting (SC) state has not been thoroughly investigated, and the SC properties as well as the spin state of this high-$$H$$ SC (HHSC) phase are not well understood. In this letter, we performed AC magnetic susceptibility and nuclear magnetic resonance measurements and found that, up to 24.8 T, the HHSC state has bulk nature and is quite sensitive to the $$H$$ angle and that its SC character is different from that in the low-$$H$$ SC (LHSC) state. The dominant spin component of the spin-triplet pair is along the $$a$$ axis in the LHSC state but is changed in the HHSC state along the $$b$$ axis. Our results indicate that $$H$$-induced multiple SC states originate from the remaining spin degrees of freedom.


Drastic change in magnetic anisotropy of UTe$$_2$$ under pressure revealed by $$^{125}$$Te-NMR

金城 克樹*; 藤林 裕己*; 仲嶺 元輝*; 北川 俊作*; 石田 憲二*; 徳永 陽; 酒井 宏典; 神戸 振作; 仲村 愛*; 清水 悠晴*; et al.

Physical Review B, 105(14), p.L140502_1 - L140502_5, 2022/04

 被引用回数:3 パーセンタイル:76.55(Materials Science, Multidisciplinary)

To investigate the normal-state magnetic properties of UTe$$_2$$ under pressure, we perform $$^{125}$$Te nuclear magnetic resonance (NMR) measurements up to 2 GPa. Below 1.2 GPa, the b-axis NMR Knight shift shows a broad maximum at the so-called $$T_{chi, max}$$ on cooling, which is consistent with the magnetization measurement under pressure. $$T_{chi, max}$$ decreases with increasing pressure and disappears at the critical pressure $$P_c$$= 1.7 GPa, above which superconductivity is destroyed.


Improving the safety of the high temperature gas-cooled reactor "HTTR" based on Japan's new regulatory requirements

濱本 真平; 清水 厚志; 猪井 宏幸; 栃尾 大輔; 本間 史隆; 澤畑 洋明; 関田 健司; 渡辺 周二; 古澤 孝之; 飯垣 和彦; et al.

Nuclear Engineering and Design, 388, p.111642_1 - 111642_11, 2022/03

 被引用回数:0 パーセンタイル:40.11(Nuclear Science & Technology)



Slow electronic dynamics in the paramagnetic state of UTe$$_2$$

徳永 陽; 酒井 宏典; 神戸 振作; 芳賀 芳範; 常盤 欣文; Opletal, P.; 藤林 裕己*; 金城 克樹*; 北川 俊作*; 石田 憲二*; et al.

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

 被引用回数:11 パーセンタイル:94.47(Physics, Multidisciplinary)



Inhomogeneous superconducting state probed by $$^{125}$$Te NMR on UTe$$_2$$

仲嶺 元輝*; 金城 克樹*; 北川 俊作*; 石田 憲二*; 徳永 陽; 酒井 宏典; 神戸 振作; 仲村 愛*; 清水 悠晴*; 本間 佳哉*; et al.

Journal of the Physical Society of Japan, 90(6), p.064709_1 - 064709_7, 2021/06

 被引用回数:14 パーセンタイル:88.05(Physics, Multidisciplinary)

UTe$$_2$$ is a recently discovered promising candidate for a spin-triplet superconductor. In contrast to conventional spin-singlet superconductivity, spin-triplet superconductivity possesses spin and angular momentum degrees of freedom. We previously reported that the shoulder signal appears in NMR spectra below the superconducting (SC) transition temperature $$T_c$$ in $$H//b$$, and a slight decrease in the Knight shift along the $$b$$ and $$c$$ axes ($$K_{rm b}$$ and $$K_{rm c}$$, respectively) below $$T_c$$ at a low magnetic field $$H$$. Although the decrease in $$K_{rm c}$$ vanished above 5.5 T, the decrease in $$K_{rm b}$$ was independent of $$H$$ up to 6.5 T. To clarify the origin of the shoulder signal and the trace of the decrease in $$K_{rm b}$$, we compared the $$^{125}$$Te-NMR spectra obtained when $$H//b$$ and $$H//c$$ and measured the $$^{125}$$Te-NMR spectra for $$H//b$$ up to 14.5 T.


Anisotropic response of spin susceptibility in the superconducting state of UTe$$_2$$ probed with $$^{125}$$Te-NMR measurement

仲嶺 元輝*; 金城 克樹*; 北川 俊作*; 石田 憲二*; 徳永 陽; 酒井 宏典; 神戸 振作; 仲村 愛*; 清水 悠晴*; 本間 佳哉*; et al.

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

 被引用回数:27 パーセンタイル:94.28(Materials Science, Multidisciplinary)

To investigate spin susceptibility in a superconducting (SC) state, we measured the $$^{125}$$Te-NMR Knight shifts at magnetic fields ($$H$$) up to 6.5 T along the $$b$$ and $$c$$ axes of single-crystal UTe$$_2$$, a promising candidate for a spin-triplet superconductor. In the SC state, the Knight shifts along the $$b$$ and $$c$$ axes ($$K_{rm b}$$ and $$K_{rm c}$$, respectively) decreased slightly, and the decrease in $$K_{rm b}$$ was almost constant up to 6.5 T. The reduction in $$K_{rm c}$$ decreased with increasing $$H$$, and $$K_{rm c}$$ was unchanged through the SC transition temperature at 5.5 T, excluding the possibility of spin-singlet pairing. Our results indicate that spin susceptibilities along the $$b$$ and $$c$$ axes slightly decrease in the SC state in low $$H$$, and the $$H$$ response of SC spin susceptibility is anisotropic on the $$bc$$ plane.


Superconducting properties of heavy fermion UTe$$_2$$ revealed by $$^{125}$$Te-nuclear magnetic resonance

仲嶺 元輝*; 北川 俊作*; 石田 憲二*; 徳永 陽; 酒井 宏典; 神戸 振作; 仲村 愛*; 清水 悠晴*; 本間 佳哉*; Li, D.*; et al.

Journal of the Physical Society of Japan, 88(11), p.113703_1 - 113703_4, 2019/11

 被引用回数:57 パーセンタイル:95.37(Physics, Multidisciplinary)

We have performed the $$^{125}$$Te-nuclear magnetic resonance (NMR) measurement in the field along the $$b$$ axis on the newly discovered superconductor UTe$$_2$$, which is a candidate of a spin-triplet superconductor. The nuclear spin-lattice relaxation rate divided by temperature 1/$$T_{1}T$$ abruptly decreases below a superconducting (SC) transition temperature $$T_{rm c}$$ without showing a coherence peak, indicative of UTe$$_2$$ being an unconventional superconductor. It was found that the temperature dependence of 1/$$T_{1}T$$ in the SC state cannot be understood by a single SC gap behavior but can be explained by a two SC gap model. The Knight shift, proportional to the spin susceptibility, decreases below $$T_{rm c}$$, but the magnitude of the decrease is much smaller than the decrease expected in the spin-singlet pairing. Rather, the small Knight-shift decrease as well as the absence of the Pauli-depairing effect can be interpreted by the spin triplet scenario.


Effect of copper addition on precipitation behavior near grain boundary in Al-Zn-Mg alloy

松田 健二*; 安元 透*; Bendo, A.*; 土屋 大樹*; Lee, S.*; 西村 克彦*; 布村 紀男*; Marioara, C. D.*; Lervik, A.*; Holmestad, R.*; et al.

Materials Transactions, 60(8), p.1688 - 1696, 2019/08

 被引用回数:13 パーセンタイル:63.15(Materials Science, Multidisciplinary)



$$^{125}$$Te-NMR study on a single crystal of heavy fermion superconductor UTe$$_2$$

徳永 陽; 酒井 宏典; 神戸 振作; 服部 泰佑; 比嘉 野乃花; 仲嶺 元輝*; 北川 俊作*; 石田 憲二*; 仲村 愛*; 清水 悠晴*; et al.

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

 被引用回数:56 パーセンタイル:95.09(Physics, Multidisciplinary)

最近新たに発見された重い電子系超伝導体UTe$$_2$$$$^{125}$$Te-NMRによる研究について報告する。単結晶試料を用い$$^{125}$$Te-NMRのKnight shift $$K$$およびスピン-格子緩和率$$1/T_1$$の測定を行なった。その結果、20K以上の常磁性相において静的および動的帯磁率のどちらもが弱いIsing型の異方性を持つことを確認した。一方、20K以下の低温ではa軸方向に磁場をかけた場合にスピン-スピン緩和率$$1/T_2$$の強い発散が見られることがわかった。このことは低温でa軸方向に強い縦型のスピン揺らぎが発達していることを示唆している。


Characterisation of structural similarities of precipitates in Mg-Zn and Al-Zn-Mg alloys systems

Bendo, A.*; 前田 朋克*; 松田 健二*; Lervik, A.*; Holmestad, R.*; Marioara, C. D.*; 西村 克彦*; 布村 紀男*; 戸田 裕之*; 山口 正剛; et al.

Philosophical Magazine, 99(21), p.2619 - 2635, 2019/07

 被引用回数:26 パーセンタイル:84.71(Materials Science, Multidisciplinary)

High angle annular dark field scanning transmission electron microscopy has been employed to observe precipitate structures in Al-Zn-Mg and Mg-Zn alloys. $$eta_{1}$$ precipitate structures in Al-Zn-Mg are commonly formed by MgZn$$_2$$ Penrose bricks, but also frequently observed to incorporate Mg$$_6$$Zn$$_7$$ elongated hexagons via two different modes. Tilings of MgZn$$_2$$ and Mg$$_6$$Zn$$_7$$ building blocks in both $$beta'_{1}$$ in Mg-Zn and $$eta_{1}$$ in Al-Zn-Mg alloys, create overall patterns which deviate from the chemical and structural configuration of solely monoclinic Mg$$_4$$Zn$$_7$$ or MgZn$$_2$$ unit cells. Precipitate morphologies were found to be correlated to their internal sub-unit cell arrangements, especially to Mg$$_6$$Zn$$_7$$ elongated hexagons.


Investigation of absorption characteristics for thermal-load fluctuation using HTTR

栃尾 大輔; 本多 友貴; 佐藤 博之; 関田 健司; 本間 史隆; 澤畑 洋明; 高田 昌二; 中川 繁昭

Journal of Nuclear Science and Technology, 54(1), p.13 - 21, 2017/01

 被引用回数:1 パーセンタイル:10.97(Nuclear Science & Technology)



HTTRを用いた熱負荷変動試験(非核加熱試験); 温度過渡に対する高温ガス炉システム応答特性の確認

本多 友貴; 栃尾 大輔; 中川 繁昭; 関田 健司; 本間 史隆; 澤畑 洋明; 佐藤 博之; 坂場 成昭; 高田 昌二

JAEA-Technology 2016-016, 16 Pages, 2016/08




Spin model of O$$_{2}$$-based magnet in a nanoporous metal complex

左右田 稔*; 本間 勇紀*; 高見澤 聡*; 河村 聖子; 中島 健次; 益田 隆嗣*

Journal of the Physical Society of Japan, 85(3), p.034717_1 - 034717_9, 2016/03

 被引用回数:1 パーセンタイル:11.74(Physics, Multidisciplinary)

ナノポーラス金属化合物Cu-${{it trans}}$-1,4-cyclohexanedicarboxylic acid (Cu-CHD)に吸着させた酸素分子について、この系で実現している酸素分子磁石の様相を探るため中性子非弾性散乱実験を行った。その結果、これまで得られている磁化曲線等を説明可能な微視的パラメーターを得ることができた。


CERL主加速器クライオモジュール運転の現状; 大電流ビーム運転時における空洞内の現象理解に向けて

沼田 直人*; 浅川 智幸*; 阪井 寛志*; 梅森 健成*; 古屋 貴章*; 篠江 憲治*; 江並 和宏*; 江木 昌人*; 坂中 章悟*; 道園 真一郎*; et al.

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (インターネット), p.566 - 570, 2015/09




本間 史隆; 平戸 洋次; 齋藤 賢司

JAEA-Technology 2014-010, 64 Pages, 2014/05




Development of operation and maintenance technology for HTGRs by using HTTR (High Temperature engineering Test Reactor)

清水 厚志; 川本 大樹; 栃尾 大輔; 齋藤 賢司; 澤畑 洋明; 本間 史隆; 古澤 孝之; 七種 明雄; 高田 昌二; 篠崎 正幸

Nuclear Engineering and Design, 271, p.499 - 504, 2014/05

 被引用回数:5 パーセンタイル:43.81(Nuclear Science & Technology)


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