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Ishida, Takekazu*; Vu, TheDang*; Shishido, Hiroaki*; Aizawa, Kazuya; Oku, Takayuki; Oikawa, Kenichi; Harada, Masahide; Kojima, Kenji M*; Miyajima, Shigeyuki*; Koyama, Tomio*; et al.
Journal of Low Temperature Physics, 214(3-4), p.152 - 157, 2024/02
Times Cited Count：0 Percentile：0.02(Physics, Applied)
single crystals based on Bragg-dip analysis using a delay-line superconducting sensorShishido, Hiroaki*; Vu, TheDang*; Aizawa, Kazuya; Kojima, Kenji M*; Koyama, Tomio*; Oikawa, Kenichi; Harada, Masahide; Oku, Takayuki; Soyama, Kazuhiko; Miyajima, Shigeyuki*; et al.
Journal of Applied Crystallography, 56(4), p.1108 - 1113, 2023/08
Times Cited Count：0 Percentile：0.02(Chemistry, Multidisciplinary)Shishido, Hiroaki*; Nishimura, Kazuma*; Vu, TheDang*; Aizawa, Kazuya; Kojima, Kenji M*; Koyama, Tomio*; Oikawa, Kenichi; Harada, Masahide; Oku, Takayuki; Soyama, Kazuhiko; et al.
IEEE Transactions on Applied Superconductivity, 31(9), p.2400505_1 - 2400505_5, 2021/12
Times Cited Count：0 Percentile：0(Engineering, Electrical & Electronic)In this study, we employed a superconducting detector, current-biased kinetic-inductance detector (CB-KID) for neutron imaging using a pulsed neutron source. We employed the delay-line method, and high spatial resolution imaging with only four reading channels was achieved. We also performed wavelength-resolved neutron imaging by the time-of-flight method. We obtained the neutron transmission images of a Gd-Al alloy sample, inside which single crystals of GdAl were grown, using the delay-line CB-KID. Single crystals were well imaged, in both shapes and distributions, throughout the Al-Gd alloy. We identified Gd nuclei via neutron transmissions that exhibited characteristic suppression above the neutron wavelength of 0.03 nm. In addition, the 
Gd resonance dip, a dip structure of the transmission caused by the nuclear reaction between an isotope and neutrons, was observed even when the number of events was summed over a limited area of 15 
m 
12 m. Gd selective imaging was performed using the resonance dip of Gd, and it showed clear Gd distribution even with a limited neutron wavelength range of 1 pm.
Vu, TheDang; Shishido, Hiroaki*; Aizawa, Kazuya; Kojima, Kenji M*; Koyama, Tomio*; Oikawa, Kenichi; Harada, Masahide; Oku, Takayuki; Soyama, Kazuhiko; Miyajima, Shigeyuki*; et al.
Nuclear Instruments and Methods in Physics Research A, 1006, p.165411_1 - 165411_8, 2021/08
Times Cited Count：1 Percentile：18.91(Instruments & Instrumentation)Vu, TheDang; Shishido, Hiroaki*; Kojima, Kenji M*; Koyama, Tomio*; Oikawa, Kenichi; Harada, Masahide; Miyajima, Shigeyuki*; Oku, Takayuki; Soyama, Kazuhiko; Aizawa, Kazuya; et al.
Superconductor Science and Technology, 34(1), p.015010_1 - 015010_10, 2021/01
Times Cited Count：3 Percentile：27.71(Physics, Applied)Shishido, Hiroaki*; Nishimura, Kazuma*; Vu, TheDang*; Kojima, Kenji M*; Koyama, Tomio*; Oikawa, Kenichi; Harada, Masahide; Miyajima, Shigeyuki*; Hidaka, Mutsuo*; Oku, Takayuki; et al.
Journal of Physics; Conference Series, 1590, p.012033_1 - 012033_8, 2020/10
Times Cited Count：0 Percentile：0.01(Engineering, Electrical & Electronic)Vu, TheDang; Nishimura, Kazuma*; Shishido, Hiroaki*; Harada, Masahide; Oikawa, Kenichi; Miyajima, Shigeyuki*; Hidaka, Mutsuo*; Oku, Takayuki; Soyama, Kazuhiko; Aizawa, Kazuya; et al.
Journal of Physics; Conference Series, 1590, p.012036_1 - 012036_9, 2020/07
Times Cited Count：0 Percentile：0.01(Engineering, Electrical & Electronic)Iizawa, Yuki*; Shishido, Hiroaki*; Nishimura, Kazuma*; Vu, TheDang*; Kojima, Kenji M*; Koyama, Tomio*; Oikawa, Kenichi; Harada, Masahide; Miyajima, Shigeyuki*; Hidaka, Mutsuo*; et al.
Superconductor Science and Technology, 32(12), p.125009_1 - 125009_8, 2019/12
Times Cited Count：13 Percentile：59.07(Physics, Applied)
B converterVu, TheDang; Iizawa, Yuki*; Nishimura, Kazuma*; Shishido, Hiroaki*; Kojima, Kenji*; Oikawa, Kenichi; Harada, Masahide; Miyajima, Shigeyuki*; Hidaka, Mutsuo*; Oku, Takayuki; et al.
Journal of Physics; Conference Series, 1293, p.012051_1 - 012051_9, 2019/10
Times Cited Count：5 Percentile：93.41(Materials Science, Multidisciplinary)Machida, Masahiko; Kobayashi, Keita; Koyama, Tomio*
Physica C, 491, p.44 - 46, 2013/08
Times Cited Count：1 Percentile：4.97(Physics, Applied)no abstracts in English
Matsumoto, Hideki*; Koyama, Tomio*; Machida, Masahiko; Ota, Yukihiro*; Yamada, Susumu
Physica C, 491, p.40 - 43, 2013/08
Times Cited Count：2 Percentile：10.3(Physics, Applied)no abstracts in English
Koyama, Tomio*; Matsumoto, Hideki*; Ota, Yukihiro*; Machida, Masahiko
Physica C, 491, p.20 - 23, 2013/08
Times Cited Count：0 Percentile：0(Physics, Applied)no abstracts in English
Koyama, Tomio*; Machida, Masahiko
Physica C, 484, p.100 - 103, 2013/01
Times Cited Count：5 Percentile：25.2(Physics, Applied)no abstracts in English
Machida, Masahiko; Ota, Yukihiro*; Koyama, Tomio*; Matsumoto, Hideki*
Journal of Physics; Conference Series, 393, p.012013_1 - 012013_8, 2012/09
Times Cited Count：1 Percentile：43.52(Physics, Multidisciplinary)Since the discovery of intrinsic Josephson effects in High-Tc cuprate superconductors, a tremendous number of theoretical and experimental studies have been made to clarify the coupling nature between stacked junctions. The reason comes from an expectation that Josephson junctions stacked in atomic-scale synchronize and high-power electromagnetic wave radiates. Consequently, two types of couplings, called "inductive and capacitive couplings" have been so far established. On the basis of the inductive coupling, several papers suggested that THz high-power emission is possible by using Josephson vortex flow states in the presence of layer parallel magnetic field and c-axis transport current. However, there has been no clear evidence of the emission in vortex flow states, although a few works found out only the sign. Afterwards, Ozyuzer et al., reported that they successfully observe a clear emission from intrinsic Josephson junctions. The situation was rather an unexpected one, since the magnetic field is not applied and the employed size is much larger than the experimental trends at that time. In this presentation, we review a history of the quest of the high power electromagnetic wave emission from intrinsic Josephson stacks before and after the Ozyuzer's work from a theoretical and numerical view. Especially, we would like to emphasize that direct numerical simulation techniques on multi-scale dynamical problems between inside and outside the junction have fully developed by authors.
Ota, Yukihiro*; Kobayashi, Keita; Machida, Masahiko; Koyama, Tomio*; Nori, F.*
Physics Procedia, 27, p.352 - 355, 2012/00
Times Cited Count：3 Percentile：73.67(Physics, Applied)no abstracts in English
Ota, Yukihiro; Machida, Masahiko; Koyama, Tomio*
Physica C, 471(21-22), p.760 - 762, 2011/11
Times Cited Count：0 Percentile：0(Physics, Applied)We construct a theory of dynamical behavior in intrinsic Josephson junction stacks (IJJ's) with multi-gap superconducting layers, motivated by recent discovery rush of highly-anisotropic iron-based superconductors with a thick perovskite block layers. The theory predicts the existence of two kinds of phase modes, one of which is the Josephson plasma mode and other of which is the Leggett's mode. The IJJ's with multiple tunneling channels have a novel energy scale, inter-band Josephson coupling on each superconducting layer which generates a mass of the Leggett's mode. We discuss a cooperative phenomena induced by such a coupling in addition to capacitive and inductive couplings between the superconducting layers.
Ota, Yukihiro; Machida, Masahiko; Koyama, Tomio*
Physica C, 470(Suppl.1), p.S489 - S490, 2010/12
Times Cited Count：0 Percentile：0(Physics, Applied)We microscopically study inter-grain Josephson current in iron-pnictide superconductors. The theoretical examination predicts that the inter-grain Josephson current is significantly reduced by 
-wave symmetry as the incoherent tunneling process becomes dominant and the density of states and the gap amplitude between two bands are identical. In addition, we suggest important points to improve the inter-grain critical current density.
Ota, Yukihiro; Machida, Masahiko; Koyama, Tomio*; Matsumoto, Hideki*
Physica C, 470(Suppl.1), p.S882 - S883, 2010/12
Times Cited Count：1 Percentile：6.48(Physics, Applied)We construct a theory of a heterotic Josephson junction between single- and two-gap superconductors. The theory predicts the presence of in-phase and out-of-phase collective modes of superconducting phases. The former is the Josephson plasma mode, and the latter is a counterpart of Leggett's mode in Josephson junctions. A signature for -wave superconductivity is a drastic reduction of the frequency of the Josephson plasma mode. We also show that the magnetic field distribution of the Josephson vortex for -wave superconductivity is more enlarged than that for s-wave without sign change between the order parameters.
Ota, Yukihiro; Machida, Masahiko; Koyama, Tomio*
Journal of Physics; Conference Series, 248, p.012090_1 - 012090_8, 2010/11
Since the discovery of iron-based superconductors, Josephson junctions including such new materials have been intensively studied in order to explore their pairing symmetry and application potential. One of interesting features of this type of materials is the presence of multiple (more than two) bands on Fermi surface and their contributions to superconductivity. As a result, iron-based superconductor junctions are possible to have multiple tunneling channels between the superconducting electrodes. In this paper, we show a theory of Josephson junctions with multigap superconductors. We discuss how the relative fluctuations between multiple gaps and the pairing symmetry modify the Shapiro steps.
Machida, Masahiko; Ota, Yukihiro; Sasa, Narimasa; Koyama, Tomio*; Matsumoto, Hideki*
Journal of Physics; Conference Series, 248, p.012037_1 - 012037_8, 2010/11
Times Cited Count：9 Percentile：90.88(Nanoscience & Nanotechnology)no abstracts in English
