研究者詳細 - 村岡　祐治

論文 - 村岡　祐治

分割表示 184 件中 101 - 120 件目／全件表示 >>

Superconducting Gap and Valence Band of Mg10Ir19B16 Studied by Laser and Synchrotron Photoemission Spectroscopy 査読

Rikiya Yoshida, Hiroyuki Okazaki, Keisuke Iwai, Kengo Noami, Takayuki Muro, Mario Okawa, Kyoko Ishizaka, Shik Shin, Zheng Li, Jianlin Luo, Guo-qing Zheng, Tamio Oguchi, Masaaki Hirai, Yuji Muraoka, Takayoshi Yokoya

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 78 ( 3 ) 034705 2009年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

We report the results of first photoemission spectroscopy on a newly discovered noncentrosymmetric superconductor Mg10Ir19B16. We measured the valence band structure of Mg10Ir19B16 using soft X-ray photoemission technique and found that the first principal calculation explains our observation well. In the bulk-sensitive laser-excited photoemission study, we observed that the intensity at the Fermi level decreases as we lower the sample temperature, indicative of the opening of superconducting energy gap. Using Dynes' function, we performed fitting analysis on the spectra of superconducting state.

DOI： 10.1143/JPSJ.78.034705

Web of Science

researchmap

Effect of UV light irradiation in SnO2 thin film 査読

Naoko Takubo, Yuji Muraoka, Zenji Hiroi

LXIII YAMADA CONFERENCE ON PHOTO-INDUCED PHASE TRANSITION AND COOPERATIVE PHENOMENA (PIPT3) 148 012025 2009年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOP PUBLISHING LTD

We observed a drastic increase in conductivity up to three orders of magnitude as a result of a photo-induced effect at the surface in a tin dioxide (SnO2) thin film. The oxygen-atmosphere effect and the light-intensity dependence of conductivity change were also experimentally studied. The experimental results indicate that the conductivity increase was caused by photo-induced oxygen desorption at the surface of the thin film.

DOI： 10.1088/1742-6596/148/1/012025

Web of Science

researchmap

Fully gapped superconductivity and strong electron correlations in the -pyrochlore KOs2O6 査読

Y. Kasahara, Y. Shimono, T. Kato, K. Hashimoto, T. Shibauchi, Y. Matsuda, S. Yonezawa, Y. Muraoka, J. Yamaura, Y. Nagao, Z. Hiroi

J. Phys. Chem.Solids 69 ( 12 ) 3228 - 3231 2008年12月

Electronic Structure of Noncentrosymmetric Superconductor Li-2(PdxPt1-x)(3)B Studied by Photoemission Spectroscopy 査読

Rikiya Yoshida, Hiroyuki Okazaki, Mitsutoshi Tajima, Takayuki Muro, Izumi Hase, Kozo Okada, Hiroyuki Takeya, Kazuto Hirata, Masaaki Hirai, Yuji Muraoka, Takayoshi Yokoya

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 ( 10 ) 104701 2008年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

We have performed x-ray photoemission spectroscopy on the system of noncentrosymmetric Superconductor, Li-2(PdxPt1-x)(3)B. For Li2Pt3B, we found two major peaks with two other weak components, and the band calculations were in agreement with the observation. The assignment of valence band features using the calculated partial density of states determined that Pt 5d and B 2p contribute to the density of states at the Fermi level. The effect of antisymmetric spin-orbit coupling on the band Structure might have been probed. and the analysis on the effect of Pt incorporation into the system indicates the smooth evolution of electronic structures. We presented the measurements of core levels (Pd 3d, Pt 4f, and B 1s) and discussed the chemical bonding states and electronic structures from them.

DOI： 10.1143/JPSJ.77.104701

Web of Science

researchmap

Photoemission evidence for a Mott-Hubbard metal-insulator transition in VO(2) 査読

R. Eguchi, M. Taguchi, M. Matsunami, K. Horiba, K. Yamamoto, Y. Ishida, A. Chainani, Y. Takata, M. Yabashi, D. Miwa, Y. Nishino, K. Tamasaku, T. Ishikawa, Y. Senba, H. Ohashi, Y. Muraoka, Z. Hiroi, S. Shin

PHYSICAL REVIEW B 78 ( 7 ) 075115 2008年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

The temperature (T)-dependent metal-insulator transition (MIT) in VO(2) is investigated using bulk sensitive hard-x-ray (similar to 8 keV) valence-band, core-level, and V 2p-3d resonant photoemission spectroscopies (PESs). The valence-band and core-level spectra are compared with full-multiplet cluster model calculations including a coherent screening channel. Across the MIT, V 3d spectral weight transfer from the coherent (3d(1)(C) under bar final) states at Fermi level to the incoherent (3d(0)+3d(1)(L) under bar final) states, corresponding to the lower Hubbard band, leads to gap formation. The spectral shape changes in V 1s and V 2p core levels as well as the valence band are nicely reproduced from cluster model calculations, providing electronic structure parameters. Resonant PES finds that the 3d(1)(L) under bar states resonate across the V 2p-3d threshold in addition to the 3d(0) and 3d(1)(C) under bar states. The results support a Mott-Hubbard transition picture for the first-order MIT in VO(2).

DOI： 10.1103/PhysRevB.78.075115

Web of Science

researchmap

Preparation and characterization of epitaxial Fe(2-x)Ti(x)O(3) films with various Ti concentrations (0.5 < x < 1.0) 査読

Takada M. Nakanishi, T. Fujii, J. Takada, Y. Muraoka

104 ( 3 ) 033713 2008年8月

Full-gap superconductivity with strong electron correlations in the -pyrochlore KOs2O6 査読

Y. Kasahara, Y. Shimono, T. Kato, K. Hashimoto, T. Shibauchi, Y. Matsuda, S. Yonezawa, Y. Muraoka, J. Yamaura, Y. Nagao, Z. Hiroi

Physica B 403 ( 5-9 ) 1068 - 1070 2008年4月

Study of electronic structures for Fe thin films deposited on Si- and C-faces of 4H-SiC substrates by soft X-ray emission spectroscopy 査読

M. Hirai, T. Wakita, H. Okazaki, D. Koishihara, Y. Muraoka, T. Yokoya

APPLIED SURFACE SCIENCE 254 ( 1 ) 26 - 28 2007年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Silicon carbide (SiC) is a candidate material for electronic devices to operate upon crucial environment. Electronic states of silicides and/or carbide/graphite formed in metal/SiC contact system are fundamentally important from the viewpoint of device performance.
We study interface electronic structure of iron thin film deposited on silicon (Si)- and carbon (C)-face of 4H-SiC(0 0 0 1) by using a soft X-ray emission spectroscopy (SXES). For specimens of Fe (50 nm)/4H-SiC (substrate) contact systems annealed at 700 and 900 degrees C, the Si L-2,L-3 emission spectra indicate different shapes and peak energies from the substrate depending on thermal-treated temperature. The product of materials such as silicides is suggested. Further, from comparison of Si L-2,L-3 emission spectra between Si- and C-face for the same annealing temperature at 700 degrees C, it is concluded that the similar silicides and/or ternary materials are formed on the two surfaces. However for those of 900 degrees C, the film on substrate is composed of the different silicide and/or ternary materials. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apsusc.2007.07.025

Web of Science

researchmap

Interplay of superconductivity and rattling phenomena in -pyrochlore KOs2O6 studied by photoemission spectroscopy 査読

T. Shimojima, Y. Shibata, K. Ishizaka, T. Kiss, A. Chainani, T. Yokoya, T. Togashi, X.-Y. Wang, C. T. Chen, S. Watanabe, J. Yamaura, S. Yonezawa, Y. Muraoka, Z. Hiroi, T. Saitoh, S. Shin

Phys. Rev. Lett. 99 ( 11 ) 117003 2007年9月

Photoemission study of TiO2/VO2 interfaces 査読

K. Maekawa, M. Takizawa, H. Wadati, T. Yoshida, A. Fujimori, H. Kumigashira, M. Oshima, Y. Muraoka, Y. Nagao, Z. Hiroi

PHYSICAL REVIEW B 76 ( 11 ) 115121 2007年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

We have measured photoemission spectra of two kinds of TiO2-capped VO2 thin films, namely, that with a rutile-type TiO2 capping layer (r-TiO2/VO2) and that with an amorphous TiO2 capping layer (a-TiO2/VO2). Below the metal-insulator transition temperature of the VO2 thin films, similar to 300 K, TiO2 and VO2 form an interface between a band insulator with the d(0) electronic configuration and a Mott (or Mott-Peierls) insulator with the d(1) electronic configuration. Metallic states were, however, not observed at the interfaces, in contrast to the interfaces between the d(0) band insulator SrTiO3 and the d(1) Mott insulator LaTiO3. We discuss possible origins of the difference between TiO2/VO2 and SrTiO3/LaTiO3, and suggest the importance of the polarity discontinuity in the latter interface. The stronger incoherent part was observed in r-TiO2/VO2 than in a-TiO2/VO2, suggesting Ti-V atomic diffusion due to the higher deposition temperature for r-TiO2/VO2.

DOI： 10.1103/PhysRevB.76.115121

Web of Science

researchmap

Anomalous magnetic phase in an undistorted pyrochlore oxide Cd2Os2O7 induced by geometrical frustration 査読

Akihiro Koda, Ryosuke Kadono, Kazuki Ohishi, Shanta R. Saha, Wataru Higemoto, Shigeki Yonezawa, Yuji Muraoka, Zenji Hiroi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 76 ( 6 ) 063703 2007年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

We report on the muon spin rotation/relaxation study of a pyrochlore oxide, Cd2Os2O7, which exhibits a metal-insulator (MI) transition at T-MI similar or equal to 225 K without structural phase transition. It reveals strong spin fluctuation (>= 10(8) s(-1)) below the MI transition, suggesting a predominant role of geometrical spin frustration amongst Os5+ ions. Meanwhile, upon further cooling, an incommensurate spin density wave discontinuously develops below T-SDW similar or equal to 150 K. These observations strongly suggest the occurrence of an anomalous magnetic transition and associated change in the local spin dynamics in undistorted pyrochlore antiferromagnet.

DOI： 10.1143/JPSJ.76.063703

Web of Science

researchmap

Precise control of band filling in NaxCoO2 査読

Daisuke Yoshizumi, Yuji Muraoka, Yoshihiko Okamoto, Yoko Kiuchi, Jun-Ichi Yamaura, Masahito Mochizuki, Masao Ogata, Zenji Hiroi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 76 ( 6 ) 063705 2007年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

Electronic properties of the sodium cobaltate NaxCoO2 are systematically studied through a precise control of band filling. Resistivity, magnetic susceptibility and specific heat measurements are carried out on a series of high-quality polycrystalline samples prepared at 200 degrees C with Na content in a wide range of 0.35 <= x <= 0.70. It is found that dramatic changes in electronic properties take place at a critical Na concentration x* that lies between 0.58 and 0.59, which separates a Pauli paramagnetic and a Curie-Weiss metals. It is suggested that at x* the Fermi level touches the bottom of the a(1g) band at the Gamma point, leading to a crucial change in the density of states across x* and the emergence of a small electron pocket around the Gamma point for x > x*.

DOI： 10.1143/JPSJ.76.063705

Web of Science

researchmap

Electronic structure of 3d(1) configuration vanadium oxides studied by soft X-ray and hard X-ray photoemission spectroscopy 査読

R. Eguchi, M. Taguchi, M. Matsunami, K. Horiba, K. Yamamoto, A. Chainani, Y. Takata, M. Yabashi, D. Miwa, Y. Nishino, K. Tamasaku, T. Ishikawa, Y. Senba, H. Ohashi, I. H. Inoue, Y. Muraoka, Z. Hiroi, S. Shin

JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 156 421 - 425 2007年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

We investigate the electronic structure of 3d(1) configuration vanadium oxides (VO2, SrVO3 and CaVO3) using soft X-ray (SX) and hard X-ray (HX) photoemission spectroscopy (PES). The valence band spectra of VO2 in SX- and HX-PES clearly show the opening of a gap at E-F across the metal-insulator transition. Spectral changes in the V 2p and O 1s core levels were also observed. In addition, 3d(1) configuration correlated metals SrVO3 and CaVO3 are typical materials whose valence band spectra are compared with dynamical mean-field theory. The V 2p and V 1s core level HX-PES of SrVO3 and CaVO3 show clear additional well-screened features. These features originate from bulk screening by a coherent band at EF. These spectra are nicely reproduced by a cluster model calculation, indicating a difference of the parameter V* for the interaction strength between the central V 3d orbitals and the coherent band. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.elspec.2006.12.055

Web of Science

researchmap

NMR observation of rattling phonons in the pyrochlore superconductor KOs2O6 査読

M. Yoshida, K. Arai, R. Kaido, M. Takigawa, S. Yonezawa, Y. Muraoka, Z. Hiroi

PHYSICAL REVIEW LETTERS 98 ( 19 ) 197002 2007年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMERICAN PHYSICAL SOC

We report nuclear magnetic resonance studies on the beta-pyrochlore oxide superconductor KOs2O6. The nuclear relaxation at the K sites is entirely caused by fluctuations of the electric field gradient, which we ascribe to highly anharmonic low frequency oscillation (rattling) of K ions. A phenomenological analysis shows a crossover from overdamped to underdamped behavior of the rattling phonons with decreasing temperature and its sudden sharpening below the superconducting transition temperature T-c. Suppression of the Hebel-Slichter peak in the relaxation rate at the O sites below T-c also indicates strong electron-phonon coupling.

DOI： 10.1103/PhysRevLett.98.197002

Web of Science

researchmap

Impurity effects on the Ni3+ triangular lattice of Ag2NiO2 査読

H. Yoshida, Y. Muraoka, Z. Hiroi

JOURNAL OF PHYSICS-CONDENSED MATTER 19 ( 14 ) 145234 2007年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

Silver oxonickelate Ag2NiO2 is a metallic compound presenting a spin- 1/2 triangular lattice. It exhibits a structural transition at T-s = 260 K, which may be related to e(g) orbital ordering, and an antiferromagnetic transition at T-N = 55 K. Impurity effects on its magnetic and electronic properties are examined by substituting Fe for Ni in Ag2Ni1-xFexO2 ( 0 <= x <= 0.3). A Curielike enhancement in magnetic susceptibility is observed at low temperature, which implies that most Fe3+ spins behave as free spins. Moreover, a large enhancement of residual resistivity and its suppression under magnetic fields are observed. Magnetic interactions in the Ni3+ triangular lattice are discussed.

DOI： 10.1088/0953-8984/19/14/145235

Web of Science

researchmap

NMR study of -pyrochlore oxide superconductor KOs2O6 査読

M. Yoshida, K. Arai, R. Kaido, M. Takigawa, S. Yonezawa, Y. Muraoka, Z. Hiroi

J. Magn. Magn. Mater. 310 ( 2 ) 698 - 699 2007年3月

Electronic structure of VO2/TiO2 : Nb upon photocarrier injection 査読

R. Eguchi, S. Tsuda, T. Kiss, A. Chainani, Y. Muraoka, Z. Hiroi, S. Shin

PHYSICAL REVIEW B 75 ( 7 ) 073102 2007年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMERICAN PHYSICAL SOC

We study the photocarrier injected electronic structure of VO2/TiO2:Nb (equivalent to p-n junction) thin-film heterostructure using photoemission spectroscopy, across the temperature-dependent metal-insulator transition in VO2. The valence band of VO2 shifts systematically to higher binding energy upon photocarrier injection (PCI). In the insulating phase, the energy shift as a function of irradiated power matches the surface photovoltage (SPV) behavior, while in the metallic phase, the energy shift follows the SPV trend but is reduced due to recombination. The temperature dependence of the energy shift between 200 and 330 K varies nearly linearly with the SPV. The study provides evidence for hole doping from TiO2:Nb to VO2 by the PCI effect.

DOI： 10.1103/PhysRevB.75.073102

Web of Science

researchmap

Asakura et al. reply

D. Asakura, J. W. Quilty, K. Takubo, T. Mizokawa, T. Mizokawa, Y. Muraoka, Z. Hiroi

Physical Review Letters 97 2006年9月

Thermal conductivity of the pyrochlore superconductor KOs2O6: Strong electron correlations and fully gapped superconductivity 査読

Y. Kasahara, Y. Shimono, T. Shibauchi, Y. Matsuda, S. Yonezawa, Y. Muraoka, Z. Hiroi

PHYSICAL REVIEW LETTERS 96 ( 24 ) 247004 2006年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMERICAN PHYSICAL SOC

To elucidate the nature of the superconducting ground state of the geometrically frustrated pyrochlore KOs2O6 (T-c=9.6 K), the thermal conductivity was measured down to low temperatures (similar to T-c/100). We found that the quasiparticle mean free path is strikingly enhanced below a transition at T-p=7.8 K, indicating enormous electron inelastic scattering in the normal state. In magnetic fields, the conduction at T -> 0 K is nearly constant up to similar to 0.4H(c2), in contrast with the rapid growth expected for superconductors with an anisotropic gap. This unambiguously indicates a fully gapped superconductivity, in contrast with previous studies. These results highlight that KOs2O6 is unique among superconductors with strong electron correlations.

DOI： 10.1103/PhysRevLett.96.247004

Web of Science

researchmap

High-pressure effects on the superconductivity on -pyrochlore oxides AOs2O6 査読

Takaki Muramatsu, Nao Takeshita, Chikeko Terakura, Hidenori Takagi, Yoshinori Tokura, Shigeki Yonezawa, Yuji Muraoka, Zenji Hiroi

Physica B 378-80 882 - 883 2006年5月

　前のページ - 次のページ　

<村岡 祐治>

論文 - 村岡 祐治

<村岡　祐治>

論文 - 村岡　祐治