※ 半角英数字
 年 ~ 
検索結果: 107 件中 1件目~20件目を表示


Initialising ...



Initialising ...


Initialising ...


Initialising ...


Initialising ...


Initialising ...


Initialising ...


Initialising ...



Orientation mapping of YbSn$$_{3}$$ single crystals based on Bragg-dip analysis using a delay-line superconducting sensor

宍戸 寛明*; Vu, TheDang*; 相澤 一也; 小嶋 健児*; 小山 富男*; 及川 健一; 原田 正英; 奥 隆之; 曽山 和彦; 宮嶋 茂之*; et al.

Journal of Applied Crystallography, 56(5), p.1108 - 1113, 2023/08

Recent progress in high-power pulsed neutron sources has stimulated the development of the Bragg dip and Bragg edge analysis methods using a two-dimensional neutron detector with high temporal resolution to resolve the neutron energy by the time-of-flight method. A delay-line current-biased kinetic inductance detector (CB-KID) is a two-dimensional superconducting sensor with a high temporal resolution and multi-hit capability. Here, it is demonstrated that a delay-line CB-KID with a $$^{10}$$B neutron conversion layer can be applied to high-spatial-resolution neutron transmission imaging and spectroscopy up to 100 eV. Dip structures are observed in the transmission spectra of YbSn$$_{3}$$ single crystals, induced by Bragg diffraction and nuclear resonance absorption. The orientation mapping of YbSn$$_{3}$$ crystals is successfully drawn based on the analysis of observed Bragg dip positions in the transmission spectra.


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.


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.


The Damage analysis for irradiation tolerant spin-driven thermoelectric device based on single-crystalline Y$$_3$$Fe$$_5$$O$$_{12}$$/Pt heterostructures

家田 淳一; 岡安 悟; 針井 一哉*; 小畠 雅明; 吉井 賢資; 福田 竜生; 石田 真彦*; 齊藤 英治

IEEE Transactions on Magnetics, 58(8), p.1301106_1 - 1301106_6, 2022/08

 被引用回数:1 パーセンタイル:30.29(Engineering, Electrical & Electronic)



Unconventional superconductivity in UTe$$_2$$

青木 大*; Brison, J.-P.*; Flouquet, J.*; 石田 憲二*; Knebel, G.*; 徳永 陽; 柳瀬 陽一*

Journal of Physics; Condensed Matter, 34(24), p.243002_1 - 243002_41, 2022/06

 被引用回数:36 パーセンタイル:91.76(Physics, Condensed Matter)

The novel spin-triplet superconductor candidate UTe$$_2$$ attracted enormous attention. We review key experimental and theoretical progress which has been achieved in different laboratories. UTe$$_2$$ has been expected to be close to a ferromagnetic instability, showing many similarities to the U-based ferromagnetic superconductors, URhGe and UCoGe. The competition between different types of magnetic interactions and the duality between the local and itinerant character of the 5 f Uranium electrons, as well as the shift of the U valence appear as key parameters in the rich phase diagrams discovered recently under extreme conditions like low temperature, high magnetic field, and pressure. We discuss macroscopic and microscopic experiments at low temperature to clarify the normal phase properties at ambient pressure for field applied along the three axis of this orthorhombic structure.


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.


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)



High spatial resolution neutron transmission imaging using a superconducting two-dimensional detector

宍戸 寛明*; 西村 和真*; Vu, TheDang*; 相澤 一也; 小嶋 健児*; 小山 富男*; 及川 健一; 原田 正英; 奥 隆之; 曽山 和彦; et al.

IEEE Transactions on Applied Superconductivity, 31(9), p.2400505_1 - 2400505_5, 2021/12

 被引用回数:0 パーセンタイル:0(Engineering, Electrical & Electronic)

中性子イメージングは、重金属に対する高透過性、軽元素に対する高感度、同位体と中性子との特異な核反応による同位体選択性などの中性子ビームの特徴を活かした非破壊検査の有力な手段の一つである。本研究では、超伝導検出器である電流バイアス運動インダクタンス検出器(CB-KID)を用いて、パルス中性子源を用いた飛行時間法による波長分解中性子イメージングを行った。遅延時間型CB-KIDを用いて、GdAl$$_{3}$$単結晶を成長させたGd-Al合金試料の中性子透過像を取得した。その結果、単結晶はAl-Gd合金全体に渡って、形状,分布ともに良好に観察することができた。また、中性子の波長0.03nm以上でGdによる特徴的な中性子の吸収を確認した。さらに、15$$mu$$m$$ times$$ 12$$mu$$mという限られた検出面で、同位体と中性子の核反応によって生じる$$^{155}$$Gd共鳴ディップを観測することができた。また、$$^{155}$$Gdの共鳴ディップを用いてGd選択的イメージングを行ったところ、中性子の波長幅が1pmという限られた範囲で、明確なGd核の元素選択イメージング像を取得することに成功した。


Hybridization of Bogoliubov quasiparticles between adjacent CuO$$_2$$ layers in the triple-layer cuprate Bi$$_2$$Sr$$_2$$Ca$$_2$$Cu$$_3$$O$$_{10+delta}$$ studied by angle-resolved photoemission spectroscopy

出田 真一郎*; Johnston, S.*; 吉田 鉄平*; 田中 清尚*; 森 道康; 安齋 太陽*; 井野 明洋*; 有田 将司*; 生天目 博文*; 谷口 雅樹*; et al.

Physical Review Letters, 127(21), p.217004_1 - 217004_6, 2021/11

 被引用回数:1 パーセンタイル:34.04(Physics, Multidisciplinary)

Hybridization of Bogoliubov quasiparticles (BQPs) between the CuO$$_2$$ layers in the triple-layer cuprate high-temperature superconductor Bi$$_2$$Sr$$_2$$Ca$$_2$$Cu$$_3$$O$$_{10+delta}$$ is studied by angle-resolved photoemission spectroscopy (ARPES). In the superconducting state, an anti-crossing gap opens between the outer- and inner-BQP bands, which we attribute primarily to interlayer single-particle hopping with possible contributions from interlayer Cooper pairing. We find that the $$d$$-wave superconducting gap of both BQP bands smoothly develops with momentum without abrupt jump in contrast to a previous ARPES study. Hybridization between the BQPs also gradually increases in going from the off-nodal to the anti-nodal region, which is explained by the momentum-dependence of the interlayer single-particle hopping. As possible mechanisms for the enhancement of the superconducting transition temperature, the hybridization between the BQPs, as well as the combination of phonon modes of the triple CuO$$_2$$ layers and spin fluctuations are discussed.


Practical tests of neutron transmission imaging with a superconducting kinetic-inductance sensor

Vu, TheDang; 宍戸 寛明*; 相澤 一也; 小嶋 健児*; 小山 富男*; 及川 健一; 原田 正英; 奥 隆之; 曽山 和彦; 宮嶋 茂之*; et al.

Nuclear Instruments and Methods in Physics Research A, 1006, p.165411_1 - 165411_8, 2021/08

 被引用回数:0 パーセンタイル:0.02(Instruments & Instrumentation)

We found that the sizes of the Gd islands determined from the transmission image correlated strongly with those determined from the SEM image. We demonstrated the CB-KID could be used to identify (1) tiny voids in a thermally sprayed continuous Gd$$_2$$O$$_3$$ film in and (2) various mosaic morphologies and different eutectic microstructures in Wood's metal samples. The fact that the CB-KID system could be used to identify features of samples with a wide distribution of sizes and thicknesses is promising for real application of the device for imaging samples of interest to material scientists. Operating the CB-KID at higher temperatures appreciably improved the efficiency for simultaneously identifying the X and Y positions of hotspots. We also compared the detection efficiency with the PHITS simulations. We now plan to improve the detection efficiency by increasing the thickness of the $$^{10}$$B neutron conversion layer


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.


Homogeneity of neutron transmission imaging over a large sensitive area with a four-channel superconducting detector

Vu, TheDang; 宍戸 寛明*; 小嶋 健児*; 小山 富男*; 及川 健一; 原田 正英; 宮嶋 茂之*; 奥 隆之; 曽山 和彦; 相澤 一也; et al.

Superconductor Science and Technology, 34(1), p.015010_1 - 015010_10, 2021/01

 被引用回数:3 パーセンタイル:32.35(Physics, Applied)

We demonstrated that a four-readout superconducting neutron imaging system shows good spatial heterogeneity and linearity using the delay-line method. We examined the precise pattern of a $$^{10}$$B-dot-array absorber and found the X-direction pitch (Px) = 250.7 um with a scatter of (Hx)= 5.4 um and the Y-direction pitch (Py)= 249.1 um with a scatter of (Hy)= 3.4 um while the $$^{10}$$B dot array was fully extended toward the X direction across the detector sensitive area. We consider that this demonstrates detection with good spatial homogeneity and conclude. The transmission-imaging system is suitable for use at pulsed neutron facilities. We also reported a clear transmission image of tiny screws and nuts, and ladybug (insect). We recognize that further efforts to improve the detection efficiency are necessary to make using the detector more practical.


Energy-resolved neutron imaging using a delay line current-biased kinetic-inductance detector

宍戸 寛明*; 西村 和真*; Vu, TheDang*; 小嶋 健児*; 小山 富男*; 及川 健一; 原田 正英; 宮嶋 茂之*; 日高 睦夫*; 奥 隆之; et al.

Journal of Physics; Conference Series, 1590, p.012033_1 - 012033_8, 2020/10

We demonstrate the development of an energy resolved neutron transmission imaging system via a solid-state superconducting detector, called current-biased kinetic-inductance detector (CB-KID). CB-KIDs comprise X and Y superconducting Nb meanderlines with Nb ground plane and a $$^{10}$$B conversion layer, which converts a neutron to two charged particles. CB-KID uses the delay-line method, and allows us to reconstruct the two-dimensional neutron transmission image of a test sample with four signal readout lines. We examined the capability of high spatial and energy (wavelength) resolved neutron transmission imaging over the sensor active area of 15 $$times$$ 15 mm$$^{2}$$ for various samples, including biological and metal ones. We also demonstrated the capability for the Bragg edge transmission and an energy-resolved neutron image in which stainless-steel specimens were discriminating from other specimens.


Tolerance of spin-Seebeck thermoelectricity against irradiation by swift heavy ions

岡安 悟; 針井 一哉*; 小畠 雅明; 吉井 賢資; 福田 竜生; 石田 真彦*; 家田 淳一; 齊藤 英治

Journal of Applied Physics, 128(8), p.083902_1 - 083902_7, 2020/08


 被引用回数:3 パーセンタイル:21.54(Physics, Applied)

The ion-irradiation tolerance of thermoelectric devices based on the spin Seebeck effect (SSE) was investigated by using 320 MeV gold ion (Au$$^{24+}$$) beams modeling cumulative damages due to fission products emitted from the surface of spent nuclear fuels. For this purpose, prototypical Pt/Y$$_3$$Fe$$_5$$O$$_{12}$$/Gd$$_3$$Ga$$_5$$O$$_{12}$$ SSE elements were irradiated with varying the dose level at room temperature and measured the SSE voltage of them. We confirmed that the thermoelectric and magnetic properties of the SSE elements are not affected by the ion-irradiation up to $$10^{10}$$ ions/cm$$^2$$ fluence and that the SSE signal is extinguished around $$10^{12}$$ ions/cm$$^2$$, in which the ion tracks almost fully cover the sample surface. We also performed the hard X-ray photoemission spectroscopy (HAXPES) measurements to understand the effects at the interface of Pt/Y$$_3$$Fe$$_5$$O$$_{12}$$. The HAXPES measurements suggest that the chemical reaction that diminishes the SSE signals is enhanced with the increase of the irradiation dose. The present study demonstrates that SSE-based devices are applicable to thermoelectric generation even in harsh environments for a long time period.


Kinetic inductance neutron detector operated at near critical temperature

Vu, TheDang; 西村 和真*; 宍戸 寛明*; 原田 正英; 及川 健一; 宮嶋 茂之*; 日高 睦夫*; 奥 隆之; 曽山 和彦; 相澤 一也; et al.

Journal of Physics; Conference Series, 1590, p.012036_1 - 012036_9, 2020/07

 被引用回数:0 パーセンタイル:0.01

Our CB-KID neutron imager detects high spatial resolution neutrons transmission images by using a delay-line technique. We found that the number of events was remarkably increased with increasing the detector temperature until close to the critical temperature Tc. We investigated the properties of CB-KID at near Tc. We observed systematic changes of neutron signals as a function of the detector temperature from 4 K to Tc. The simulations modeled the sequential physical processes for $$^{10}$$B(n,$$alpha$$)$$^{7}$$Li reactions and energy deposition by particles within CB-KID, including neutrons, $$^{4}$$He particles, $$^{7}$$Li particles, photon and electron transport.


Development of a bunch-width monitor for low-intensity muon beam below a few MeV

須江 祐貴*; 四塚 麻衣*; 二ツ川 健太*; 長谷川 和男; 飯嶋 徹*; 飯沼 裕美*; 居波 賢二*; 石田 勝彦*; 河村 成肇*; 北村 遼; et al.

Physical Review Accelerators and Beams (Internet), 23(2), p.022804_1 - 022804_7, 2020/02

低エネルギー、低インテンシティーミューオンビームのビーム進行方向のバンチ幅を測定するための破壊的モニターを開発した。このバンチ幅モニター(BWM)は、1つずつのミューオンを高い分解能で測定するためにマイクロチャンネルプレートを用いている。それに加え、タイミングウオークを抑制するために、コンスタントフラクションディスクリミネータ回路を用いている。時間分解能は精密パルスレーザーを用いて65psと測定された。この分解能は、J-PARC E34実験で要求される性能を満たしている。我々は、このBWMを用いて、高周波四重極リニアックによって加速された負ミューオニウムイオンのバンチ幅を測定した。バンチ幅54$$pm$$11nsと測定することに成功した。


Negative muonium ion production with a C12A7 electride film

大谷 将士*; 深尾 祥紀*; 二ツ川 健太*; 河村 成肇*; 的場 史朗*; 三部 勉*; 三宅 康博*; 下村 浩一郎*; 山崎 高幸*; 長谷川 和男; et al.

Journal of Physics; Conference Series, 1350, p.012067_1 - 012067_6, 2019/12

 被引用回数:2 パーセンタイル:75.02


107 件中 1件目~20件目を表示