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Iwasa, Kazuaki*; Suyama, Kazuya*; Kawamura, Seiko; Nakajima, Kenji; Raymond, S.*; Steffens, P.*; Yamada, Akira*; Matsuda, Tatsuma*; Aoki, Yuji*; Kawasaki, Ikuto; et al.
Physical Review Materials (Internet), 7(1), p.014201_1 - 014201_11, 2023/01
Times Cited Count:2 Percentile:72.03(Materials Science, Multidisciplinary)Fujimori, Shinichi; Okochi, Takuo*; Kawasaki, Ikuto*; Yasui, Akira*; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; et al.
Physical Review B, 91(17), p.174503_1 - 174503_9, 2015/05
Times Cited Count:25 Percentile:70.6(Materials Science, Multidisciplinary)The electronic structures of the ferromagnetic superconductors UGe and UCoGe in the paramagnetic phase were studied by angle-resolved photoelectron spectroscopy using soft X-rays ( = 400-500 eV). The quasi-particle bands with large contributions from U 5 states were observed in the vicinity of EF, suggesting that the U 5 electrons of these compounds have an itinerant character. Their overall band structures were explained by the band-structure calculations treating all the U 5 electrons as being itinerant. Meanwhile, the states in the vicinity of EF show considerable deviations from the results of band-structure calculations, suggesting that the shapes of Fermi surface of these compounds are qualitatively different from the calculations, possibly caused by electron correlation effect in the complicated band structures of the low-symmetry crystals. Strong hybridization between U 5 and states in UCoGe were found by the 2p-3d resonant photoemission experiment, suggesting that states have finite contributions to the magnetic, transport, and superconducting properties.
Fujimori, Shinichi; Kawasaki, Ikuto*; Yasui, Akira*; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; Yamamoto, Etsuji; et al.
JPS Conference Proceedings (Internet), 3, p.011072_1 - 011072_5, 2014/06
In this presentation, we review some of our recent photoemission studies on uranium superconductors by means of soft X-ray synchrotron radiation ARPES (SX-ARPES). Results of SX-ARPES study on URhGe and UPdAl will be presented. URhGe is a ferromagnetic superconductor with = 9.5 K and = 0.26 K while UPdAl is an antiferromagnetic superconductor with = 14 K and = 1.8 K. We have revealed the three-dimensional electronic structures of those compounds by SX-ARPES, and they are compared with those calculated by LDA.
Fujimori, Shinichi; Kawasaki, Ikuto*; Yasui, Akira*; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi*; Yamagami, Hiroshi; Haga, Yoshinori; Yamamoto, Etsuji; et al.
Physical Review B, 89(10), p.104518_1 - 104518_7, 2014/03
Times Cited Count:21 Percentile:65.2(Materials Science, Multidisciplinary)The electronic structure of the ferromagnetic superconductor URhGe in the paramagnetic phase has been studied by angle-resolved photoelectron spectroscopy using soft X rays ( = 595-700 eV). Dispersive bands with large contributions from U 5 states were observed in the ARPES spectra, and form Fermi surfaces. The band structure in the paramagnetic phase is partly explained by the band-structure calculation treating all U 5 electrons as being itinerant, suggesting that an itinerant description of U 5 states is a good starting point for this compound. On the other hand, there are qualitative disagreements especially in the band structure near the Fermi level ( 0.5 eV). The experimentally observed bands are less dispersive than the calculation, and the shape of the Fermi surface is different from the calculation. The changes in spectral functions due to the ferromagnetic transition were observed in bands near the Fermi level, suggesting that the ferromagnetism in this compound has an itinerant origin.
Nakajima, Nakako*; Brunton, H.*; Watanabe, Ritsuko; Shrikhande, A.*; Hirayama, Ryoichi*; Matsufuji, Naruhiro*; Fujimori, Akira*; Murakami, Takeshi*; Okayasu, Ryuichi*; Jeggo, P.*; et al.
PLOS ONE (Internet), 8(8), p.e70107_1 - e70107_14, 2013/08
Times Cited Count:63 Percentile:91.05(Multidisciplinary Sciences)Heavy particle irradiation can produce complex DNA double strand breaks (DSBs) within the particle trajectory. Additionally, secondary electrons, termed delta-electrons, can create low linear energy transfer (LET) damage distant from the track. Using imaging with deconvolution, we show that at 8 hours after exposure to Fe ions, H2AX foci forming at DSBs within the particle track are large and encompass multiple smaller and closely localised foci, which we designate as clustered H2AX foci. We also identified simple H2AX foci distant from the track. They are rapidly repaired. Clustered H2AX foci induced by heavy particle radiation cause prolonged checkpoint arrest compared to simple H2AX foci. However, mitotic entry was observed when 10 clustered foci remain. Thus, cells can progress into mitosis with multiple clusters of DSBs following the traversal of a heavy particle.
Yasui, Akira*; Saito, Yuji; Fujimori, Shinichi; Kawasaki, Ikuto*; Okane, Tetsuo; Takeda, Yukiharu; Lapertot, G.*; Knebel, G.*; Matsuda, Tatsuma*; Haga, Yoshinori; et al.
Physical Review B, 87(7), p.075131_1 - 075131_6, 2013/02
Times Cited Count:6 Percentile:29.39(Materials Science, Multidisciplinary)We have performed soft X-ray angle-resolved photoemission spectroscopy (ARPES) measurements on YbRhSi and clarified its three-dimensional bulk valence-band structures. The ARPES spectra have not only Yb multiplet peaks but also a finite contribution of Yb peaks at 15 K, corresponding to the valence fluctuating behavior in this compound. This means that Yb 4f electrons in this compound have itinerant character below the . We have found that dispersions of the valence bands except the vicinity of the Yb 4f bands agree better with those of the band-structure calculation of LuRhSi than those of YbRhSi within a local-density approximation. In addition, the Yb 3d-4f resonant photoemission spectra of YbRhSi strongly suggest the existence of Yb 5d electrons in the valence band. We conclude that the charge transfer from the Yb 4f state to the Yb 5d state has an important role in the formation of the valence band of YbRhSi.
Fujimori, Shinichi; Okochi, Takuo*; Kawasaki, Ikuto; Yasui, Akira; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; et al.
Journal of the Physical Society of Japan, 81(1), p.014703_1 - 014703_9, 2012/01
Times Cited Count:37 Percentile:82.18(Physics, Multidisciplinary)High-energy-resolution core-level and valence-band photoelectron spectroscopic studies were performed for the heavy Fermion uranium compounds UGe, UCoGe, URhGe, URuSi, UNiAl, UPdAl, and UPt as well as typical localized and itinerant uranium compounds to understand the relationship between the uranium valence state and their core-level spectral line shapes. The core-level spectra of UGe, UCoGe, URhGe, URuSi, and UNiAl are rather similar to those of itinerant compounds, suggesting that U 5 electrons in these compounds are well hybridized with ligand states. On the other hand, the core-level spectra of UPdAl and UPt show considerably different spectral line shapes from those of the itinerant compounds, suggesting that U 5 electrons in UPdAl and UPt are less hybridized with ligand states, leading to the correlated nature of U 5 electrons in these compounds.
Kawasaki, Ikuto; Fujimori, Shinichi; Okane, Tetsuo; Yasui, Akira; Saito, Yuji; Yamagami, Hiroshi*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika*
Journal of the Physical Society of Japan, 80(12), p.124710_1 - 124710_5, 2011/12
Times Cited Count:6 Percentile:43.42(Physics, Multidisciplinary)We have carried out soft X-ray angle-resolved photoemission spectroscopy experiments on U(RuRh)Si, which shows antiferromagnetic (AFM) ordering at low temperatures. We have revealed that U 5 electrons contribute to the formation of the energy band as well as Fermi surface. This suggests that the AFM ordering is caused by a spin density wave of itinerant U 5 electrons. The observed band dispersion and Fermi surface are nearly identical to those of URuSi. Therefore, the AFM ordering vector = (1,0,0) can be a possible ordering vector of the hidden order phase in URuSi.
Yasui, Akira; Fujimori, Shinichi; Kawasaki, Ikuto; Okane, Tetsuo; Takeda, Yukiharu; Saito, Yuji; Yamagami, Hiroshi; Sekiyama, Akira*; Settai, Rikio*; Matsuda, Tatsuma; et al.
Physical Review B, 84(19), p.195121_1 - 195121_6, 2011/11
Times Cited Count:7 Percentile:32.89(Materials Science, Multidisciplinary)We have measured three-dimensional band structure and Fermi surfaces (FSs) of YbCuGe, which has recently become recognized as a nearly divalent Yb-based compound, by using soft X-ray angle-resolved photoemission spectroscopy. We clarified that the bands with finite Yb 4 contribution cross the Fermi level and are slightly involved in the formation of the FSs, in line with the valence-fluctuating state of YbCuGe. The obtained valence-band dispersions and the FSs are well explained by a relativistic band-structure calculation based on a local-density-approximation (LDA). These results suggest that the LDA calculation is a good starting point for understanding of the electronic state of YbCuGe as well as nearly divalent Yb-based compounds.
Okane, Tetsuo; Kawasaki, Ikuto; Yasui, Akira; Okochi, Takuo*; Takeda, Yukiharu; Fujimori, Shinichi; Saito, Yuji; Yamagami, Hiroshi; Fujimori, Atsushi; Matsumoto, Yuji*; et al.
Journal of the Physical Society of Japan, 80(Suppl.A), p.SA060_1 - SA060_3, 2011/07
Times Cited Count:1 Percentile:11.35(Physics, Multidisciplinary)Nishi, Ichiro*; Ishikado, Motoyuki; Ideta, Shinichiro*; Malaeb, W.*; Yoshida, Teppei*; Fujimori, Atsushi*; Kotani, Yoshinori*; Kubota, Masato*; Ono, Kanta*; Yi, M.*; et al.
Physical Review B, 84(1), p.014504_1 - 014504_5, 2011/07
Times Cited Count:22 Percentile:65.72(Materials Science, Multidisciplinary)We have performed an angle-resolved photoemission spectroscopy (ARPES) study of the iron-based superconductor PrFeAsO and examined the Fermi surfaces and band dispersions near the fermi level. Heavily hole-doped electronic states have been observed due to the polar nature of the cleaved surfaces. Nevertheless, we have found that the ARPES spectra basically agree with band dispersions calculated in the local density approximation (LDA) if the bandwidth is reduced by a factor of 2.5 and then the chemical potential is lowered by 70 meV. Comparison with previous ARPES results on LaFePO reveals that the energy positions of the - and -derived bands are considerably different between the two materials, which we attribute to the different pnictogen height as predicted by the LDA calculation.
Yasui, Akira; Fujimori, Shinichi; Kawasaki, Ikuto; Okane, Tetsuo; Takeda, Yukiharu; Saito, Yuji; Yamagami, Hiroshi; Sekiyama, Akira*; Settai, Rikio*; Matsuda, Tatsuma; et al.
Journal of Physics; Conference Series, 273, p.012067_1 - 012067_4, 2011/02
Times Cited Count:3 Percentile:62.76(Physics, Condensed Matter)Soft X-ray photoemission spectroscopies have been performed on YbCuGe, which is thought to be a Yb divalent system, to investigate its bulk electronic structure including Yb 4 electrons. Small but finite Yb multiplet peaks were found at 612 eV in the angle-integrated spectrum, suggesting that it is a valence fluctuation compound. An "anti-crossing" Yb 4 bands with conduction bands were observed in the angle-resolved spectrum. This is the evidence that the Yb 4 electrons form a band state through the hybridization with Ge 4 and Cu 3 electrons.
Okane, Tetsuo; Okochi, Takuo*; Takeda, Yukiharu; Fujimori, Shinichi; Yasui, Akira; Saito, Yuji; Yamagami, Hiroshi; Fujimori, Atsushi; Matsumoto, Yuji*; Sugi, Motoki*; et al.
Physica Status Solidi (B), 247(3), p.397 - 399, 2010/03
Takeda, Yukiharu; Okane, Tetsuo; Okochi, Takuo*; Saito, Yuji; Yamagami, Hiroshi; Fujimori, Atsushi*; Ochiai, Akira*
Physical Review B, 80(16), p.161101_1 - 161101_4, 2009/10
Times Cited Count:8 Percentile:36.66(Materials Science, Multidisciplinary)no abstracts in English
Okochi, Takuo*; Toshimitsu, Takafumi*; Yamagami, Hiroshi; Fujimori, Shinichi; Yasui, Akira; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Miyauchi, Yuichiro*; et al.
Journal of the Physical Society of Japan, 78(8), p.084802_1 - 084802_6, 2009/08
Times Cited Count:10 Percentile:54.6(Physics, Multidisciplinary)We have applied angle-resolved Ce 34 resonance photoemission spectroscopy to the non-centrosymmetric pressure-induced superconductor CeIrSi and obtained the 4 band-structure and Fermi surfaces. We have found that the Ce 4 states are located mainly near the Fermi level and that the photoemission intensity derived from the dispersive conduction bands across the Fermi level shows considerable resonant enhancement. In addition, the band structure and Fermi surfaces of CeIrSi are different from those of the non- reference compound, LaIrSi and the difference is well explained by the band structure calculated within the local density approximation (LDA). These results strongly suggest that the Ce 4 electrons in CeIrSi are well hybridized with conduction bands and form itinerant electronic states.
Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sato, Nozomi*; Sumita, Takayuki*; Yoneda, Akira*; Ichikawa, Takatoshi*; et al.
Journal of the Physical Society of Japan, 78(6), p.064201_1 - 064201_6, 2009/06
Times Cited Count:30 Percentile:78.34(Physics, Multidisciplinary)Decay properties of an isotope Bh and its daughter nucleus Db produced by the Cm(Na,5) reaction were studied by using a gas-filled recoil separator coupled with a position-sensitive semiconductor detector. Bh was clearly identified from the correlation of the known nuclide, Db. The obtained decay properties of Bh and Db are consistent with those observed in the 113 chain, which provided further confirmation of the discovery of 113.
Okane, Tetsuo; Okochi, Takuo*; Takeda, Yukiharu; Fujimori, Shinichi; Yasui, Akira; Saito, Yuji; Yamagami, Hiroshi; Fujimori, Atsushi; Matsumoto, Yuji*; Sugi, Motoki*; et al.
Physical Review Letters, 102(21), p.216401_1 - 216401_4, 2009/05
Times Cited Count:28 Percentile:77.12(Physics, Multidisciplinary)Okane, Tetsuo; Takeda, Yukiharu; Okamoto, Jun*; Mamiya, Kazutoshi*; Okochi, Takuo; Fujimori, Shinichi; Saito, Yuji; Yamagami, Hiroshi; Fujimori, Atsushi; Ochiai, Akira*; et al.
Journal of the Physical Society of Japan, 77(2), p.024706_1 - 024706_6, 2008/02
Times Cited Count:15 Percentile:64.38(Physics, Multidisciplinary)Okane, Tetsuo; Takeda, Yukiharu; Fujimori, Shinichi; Saito, Yuji; Okamoto, Jun*; Mamiya, Kazutoshi*; Muramatsu, Yasuji*; Fujimori, Atsushi; Ochiai, Akira*; Haga, Yoshinori; et al.
Journal of the Physical Society of Japan, 75(Suppl.), p.105 - 106, 2006/08
no abstracts in English
Okane, Tetsuo; Okamoto, Jun; Mamiya, Kazutoshi; Fujimori, Shinichi; Saito, Yuji; Muramatsu, Yasuji; Fujimori, Atsushi; Ochiai, Akira*
Physica B; Condensed Matter, 345(1-4), p.221 - 224, 2004/03
Times Cited Count:6 Percentile:34.04(Physics, Condensed Matter)Magnetic circular dichroism (MCD) has been measured at the U absorption edges of ferromagnetic uranium monochalcogenides US, USe and UTe. The MCD signals are weaker in US than in USe and UTe. Both the spin and orbital moments are increased in going from US to USe, and then reduced from USe to UTe.