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Journal Articles

Self-reconstruction of order parameter in spin-triplet superconductor UTe

Tokiwa, Yoshifumi; Opletal, P.; Sakai, Hironori; Kubo, Katsunori; Kambe, Shinsaku; Yamamoto, Etsuji; Kimata, Motoi; Awaji, Satoshi*; Sasaki, Takahiko*; Aoki, Dai*; et al.

Physical Review Letters, 135(13), p.136502_1 - 136502_6, 2025/09

https://doi.org/10.1103/z8yx-yzdh

Times Cited Count：4 Percentile：74.19(Physics, Multidisciplinary)

We investigate the effect of easy-axis metamagnetic crossover on superconductivity in UTe along the -axis through measurements of AC susceptibility, magnetization, and the magnetocaloric effect. In ultra-clean single crystals, we identify a field-induced phase transition within the superconducting state at 5.6 T, driven by metamagnetism. This transition leads to a high-field superconducting state, significantly increasing the upper critical field to 12 T. A sudden increase in entropy at the transition suggests a self-reconstruction of the order parameter, enabling multi-component superconducting states to adapt to external perturbations.

Journal Articles

Internal strain measurement by neutron diffraction under transverse compressive stress for Nb $_{3}$ Sn wires with and without Cu-Nb reinforcement

Nakamoto, Mio*; Sugano, Michinaka*; Ogitsu, Toru*; Sugimoto, Masahiro*; Taniguchi, Ryo*; Hirose, Kiyoshige*; Kawasaki, Takuro; Gong, W.; Harjo, S.; Awaji, Satoshi*; et al.

IEEE Transactions on Applied Superconductivity, 34(5), p.8400806_1 - 8400806_6, 2024/08

https://doi.org/10.1109/TASC.2024.3379124

Times Cited Count：1 Percentile：11.42(Engineering, Electrical & Electronic)

Journal Articles

Reinforcement of superconductivity by quantum critical fluctuations of metamagnetism in UTe

Tokiwa, Yoshifumi; Opletal, P.; Sakai, Hironori; Kambe, Shinsaku; Yamamoto, Etsuji; Kimata, Motoi*; Awaji, Satoshi*; Sasaki, Takahiko*; Aoki, Dai*; Haga, Yoshinori; et al.

Physical Review B, 109(14), p.L140502_1 - L140502_6, 2024/04

https://doi.org/10.1103/PhysRevB.109.L140502

Times Cited Count：9 Percentile：75.86(Materials Science, Multidisciplinary)

The normal-conducting state of the superconductor UTe is studied by entropy analysis for magnetic fields along the -axis, obtained from magnetization using the relation . We observe a strong increase in entropy with magnetic field due to metamagnetic fluctuations (spatially uniform, ). The field dependence is well described by the Hertz-Millis-Moriya theory for quantum criticality of itinerant metamagnetism. Notably, the lower bound of the quantum-critical region coincides well with the position of the minimum in the superconducting transition temperature . Hence, our results suggest that fluctuations reinforce the superconductivity.

Journal Articles

Anomalous vortex dynamics in the spin-triplet superconductor UTe

Tokiwa, Yoshifumi; Sakai, Hironori; Kambe, Shinsaku; Opletal, P.; Yamamoto, Etsuji; Kimata, Motoi*; Awaji, Satoshi*; Sasaki, Takahiko*; Yanase, Yoichi*; Haga, Yoshinori; et al.

Physical Review B, 108(14), p.144502_1 - 144502_5, 2023/10

https://doi.org/10.1103/PhysRevB.108.144502

Times Cited Count：12 Percentile：66.33(Materials Science, Multidisciplinary)

The vortex dynamics in the spin-triplet superconductor, UTe, are studied by measuring the DC electrical resistivity with currents along the -axis under magnetic fields along the -axis. Surprisingly, we have discovered an island region of low critical current deep inside the superconducting (SC) state, well below the SC upper critical field, attributed to a weakening of vortex pinning. Notably, this region coincides with the recently proposed intermediate-field SC state. We discuss the possibility of nonsingular vortices in the intermediate state, where SC order parameter does not vanish entirely in the vortex cores due to the mixing of multiple SC components.

Journal Articles

Field induced multiple superconducting phases in UTe along hard magnetic axis

Sakai, Hironori; Tokiwa, Yoshifumi; Opletal, P.; Kimata, Motoi*; Awaji, Satoshi*; Sasaki, Takahiko*; Aoki, Dai*; Kambe, Shinsaku; Tokunaga, Yo; Haga, Yoshinori

Physical Review Letters, 130(19), p.196002_1 - 196002_6, 2023/05

https://doi.org/10.1103/PhysRevLett.130.196002

Times Cited Count：35 Percentile：94.69(Physics, Multidisciplinary)

The superconducting (SC) phase diagram in uranium ditelluride is explored under magnetic fields () along the hard magnetic -axis using a high-quality single crystal with $T_{rm c}$ = 2.1 K. Simultaneous electrical resistivity and AC magnetic susceptibility measurements discern low- and high-field SC (LFSC and HFSC, respectively) phases with contrasting field-angular dependence. Crystal quality increases the upper critical field of the LFSC phase, but the $H^{ast}$ of T, at which the HFSC phase appears, is always the same through the various crystals. A phase boundary signature is also observed inside the LFSC phase near $H^{ast}$ , indicating an intermediate SC phase characterized by small flux pinning forces.

Journal Articles

Superconducting fluctuation effect on epitaxially layered films of superconductor NbN and half-metallic Heusler alloy Co $_{2}$ MnSi

Shigeta, Iduru*; Oku, Shuta*; Kubota, Takahide*; Kimura, Shojiro*; Seki, Takeshi*; Shinozaki, Bunju*; Awaji, Satoshi*; Takanashi, Koki; Hiroi, Masahiko*

AIP Advances (Internet), 13(2), p.025116_1 - 025116_5, 2023/02

https://doi.org/10.1063/9.0000584

Times Cited Count：1 Percentile：6.07(Nanoscience & Nanotechnology)

Journal Articles

Angular behaviour of critical current density in YBa $_{2}$ Cu $_{3}$ Oy thin films with crossed columnar defects

Sueyoshi, Tetsuro*; Sogo, Takehiro*; Nishimura, Takahiro*; Fujiyoshi, Takanori*; Mitsugi, Fumiaki*; Ikegami, Tomoaki*; Awaji, Satoshi*; Watanabe, Kazuo*; Ichinose, Ataru*; Ishikawa, Norito

Superconductor Science and Technology, 29(6), p.065023_1 - 065023_8, 2016/05

https://doi.org/10.1088/0953-2048/29/6/065023

Times Cited Count：22 Percentile：63.41(Physics, Applied)

Columnar defects (CDs) were installed into YBa $_{2}$ Cu $_{3}$ Oy thin films at the crossing angle relative to the c-axis using 200 MeV Xe ions. The width of a Jc peak occurring around B//c linearly increases with broadening the CD-crossing angle, where its shape maintains a single peak in the small angle range. The CDs crossing at 45, on the other hand, drastically change the angular behaviour of Jc around B//c, the Jc is equally elevated over the angular region from -45 to +45 in lower magnetic field, whereas the rapid reduction of the Jc around B//c occurs with increasing the magnetic field, leading to the appearance of double peaks at the irradiation angles, -45 and +45.

Journal Articles

Enhancement of critical current densities by high-pressure sintering in (Sr,K)Fe $_{2}$ As $_{2}$ PIT wires

Pyon, S.*; Tsuchiya, Yuji*; Inoue, Hiroshi*; Kajitani, Hideki; Koizumi, Norikiyo; Awaji, Satoshi*; Watanabe, Kazuo*; Tamegai, Tsuyoshi*

Superconductor Science and Technology, 27(9), p.095002_1 - 095002_7, 2014/09

https://doi.org/10.1088/0953-2048/27/9/095002

Times Cited Count：37 Percentile：77.39(Physics, Applied)

Many scientists have been trying to improve the superconductor performance of ferrous strand "((Sr,K)Fe $_{2}$ As $_{2}$ " with improvement of the dope materials and fabricating process. Especially, it is expected that heat treatment under high pressure for the strand is good for improvement of the critical current performance because it makes intercrystalline bond power in the material stronger. In past study, using some kinds of tape strand, the improvement of critical current performance could be experimentally achieved with this method. In this paper, it is shown that the author newly fabricated rounded strand and HIP (700 degrees, 4 hours, 120 MPa) was applied for it and then the critical performance was measured. The result could be achieved as 1[kA/mm $^{2}$ ]. This high value is meaningful in terms of the application for the magnet and some apparatuses.

Journal Articles

Flux pinning properties of correlated pinning at low temperatures in ErBCO films with inclined columnar defects

Awaji, Satoshi*; Namba, Masashi*; Watanabe, Kazuo*; Kai, Hideki*; Mukaida, Masashi*; Okayasu, Satoru

Journal of Applied Physics, 111(1), p.013914_1 - 013914_4, 2012/01

https://doi.org/10.1063/1.3675181

Times Cited Count：27 Percentile：68.88(Physics, Applied)

The effect of -axis correlated pinning on the critical current density $_{c}$ at low temperatures under high magnetic fields was investigated on the basis of the transport measurements of $_{c}$ and irreversibility field B $_{irr}$ properties of an ErBa $_{2}$ Cu $_{3}$ O $_{y}$ film with inclined columnar defects. The contribution of correlated pinning on $_{c}$ decreased drastically with decreasing temperature under high magnetic fields above the matching field. At low temperatures, the presence of a matching field limited the pinning force for correlated pinning, while the ratio of the maximum pinning force of the correlated pinning to the random one was proportional to the inverse of B $_{irr}$ . In order to improve the critical current properties at low temperatures under high magnetic fields, an increase in the matching field and/or the introduction of strong random pinning are effective.

Journal Articles

Cooperative behavior of the random and correlated pinning in Er123 films with columnar defects

Awaji, Satoshi*; Namba, Masashi*; Watanabe, Kazuo*; Ito, Shun*; Aoyagi, Eiji*; Kai, Hideki*; Mukaida, Masashi*; Okayasu, Satoru

IEEE Transactions on Applied Superconductivity, 21(3), p.3192 - 3195, 2011/06

https://doi.org/10.1109/TASC.2010.2089588

Times Cited Count：7 Percentile：39.56(Engineering, Electrical & Electronic)

The flux pinning behaviors for the heavy ion irradiated Er123 films are investigated based on the detailed $_{rm c}$ (, , ) properties. The double peaks of $_{rm p}$ curves for //c appear in case of the matching field of 0.3 T along -axis and 1.7 T tilted from -axis. In addition, the peaks on $_{rm c}$ () at = 0 $^{circ}$ (B//c), which originate from the columnar defects, decrease with increasing magnetic field but increase again near the irreversibility field. We found that the cooperation model of the -axis correlated and random pinning centers can describe the observed double peak behavior of $_{rm p}$ (B) and the angular dependence of $_{rm c}$ related to the correlated pinning.

Journal Articles

Stress/strain effects on industrial superconducting composites

Ito, Takayoshi; Harjo, S.; Osamura, Kozo*; Hemmi, Tsutomu; Awaji, Satoshi*; Machiya, Shutaro*; Oguro, Hidetoshi*; Nishijima, Gen*; Takahashi, Koki*; Matsui, Kunihiro; et al.

Materials Science Forum, 681, p.209 - 214, 2011/05

https://doi.org/10.4028/www.scientific.net/MSF.681.209

Times Cited Count：1 Percentile：48.75(Materials Science, Multidisciplinary)

Journal Articles

Performance tests of reactor containment structures of the HTTR

Iigaki, Kazuhiko; Sakaba, Nariaki; Kawaji, Satoshi; Iyoku, Tatsuo

Transactions of 16th International Conference on Structural Mechanics in Reactor Technology (SMiRT-16) (CD-ROM), 7 Pages, 2001/08

no abstracts in English

Journal Articles

Instrumentation and control system of the HTTR

Saito, Kenji; Homma, Fumitaka; Omata, Toru; Aono, Tetsuya; Kawaji, Satoshi; Kawasaki, Kozo; Iyoku, Tatsuo

Proceedings of International Topical Meeting on Nuclear Plant Instrumentation, Controls, and Human-Machine Interface Technologies (NPIC&HMIT 2000) (CD-ROM), 8 Pages, 2000/00

no abstracts in English

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