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Journal Articles

Evolution of the filamentary 3-Kelvin phase in Pb-Ru-Sr$$_{2}$$RuO$$_{4}$$ Josephson junctions

Kaneyasu, Hirono*; Etter, S. B.*; Sakai, Toru; Sigrist, M.*

Physical Review B, 92(13), p.134515_1 - 134515_5, 2015/10

 Times Cited Count:4 Percentile:14.69(Materials Science, Multidisciplinary)

The evolution of the 3-Kelvin superconductivity phase at the interface between Sr$$_{2}$$RuO$$_{4}$$ and Ru-metal inclusions is discussed for Pb-Ru-Sr$$_{2}$$RuO$$_{4}$$ contacts. Using the Ginzburg-Landau model, the influence of proximity-induced superconductivity in Ru on the topology of the 3-K phase is analysed. Because the s-wave order parameter in Ru favors a 3-K state of trivial topology, the onset temperature of the phase with a nontrivial topology is essentially reduced to the bulk transition temperature.

Journal Articles

Momentum dependence of Mott gap excitations in optimally doped YBa$$_2$$Cu$$_3$$O$$_{7-delta}$$ studied by resonant inelastic X-ray scattering

Ishii, Kenji; Tsutsui, Kenji*; Endo, Yasuo*; Toyama, Takami*; Kuzushita, Kaori; Inami, Toshiya; Owada, Kenji; Maekawa, Sadamichi*; Masui, Takahiko*; Tajima, Setsuko*; et al.

AIP Conference Proceedings 850, p.445 - 446, 2006/09

Mott gap excitations in the optimally doped high-$$T_{c}$$ superconductor YBa$$_2$$Cu$$_3$$O$$_{7-delta}$$ ($$T_{c}$$ = 93 K) have been studied by the resonant inelastic X-ray scattering method. Anisotropic spectra in the $$ab$$-plane are observed in a twin-free crystal. The excitation from the one-dimensional CuO chain is enhanced at 2 eV near the zone boundary of the $$b^{*}$$ direction, while the excitation from the CuO$$_2$$ plane is broad at 1.5-4 eV and almost independent of the momentum transfer. Theoretical calculation based on the one-dimensional and two-dimensional Hubbard model reproduces the observed spectra when different values of the on-site Coulomb energy are assumed. The Mott gap of the CuO chain site is found to be much smaller than that of the CuO$$_2$$ plane site.

Journal Articles

Doping Momentum dependence of charge dynamics in Nd$$_{2-x}$$Ce$$_{x}$$CuO$$_4$$ (x=0, 0.075, and 0.15) studied by Resonant inelastic X-ray scattering

Ishii, Kenji; Tsutsui, Kenji*; Endo, Yasuo*; Toyama, Takami*; Maekawa, Sadamichi*; Hoesch, M.; Kuzushita, Kaori; Inami, Toshiya; Tsubota, Masami; Yamada, Kazuyoshi*; et al.

AIP Conference Proceedings 850, p.403 - 404, 2006/09

We report a resonant inelastic X-ray scattering (RIXS) study of charge excitations in the electron-doped high-$$T_{c}$$ superconductor Nd$$_{1.85}$$Ce$$_{0.15}$$CuO$$_4$$. The intraband and interband excitations across the Fermi energy are separated for the first time by tuning the experimental conditions properly to measure charge excitations at low energy. A dispersion relation with $${mathbf q}$$-dependent width emerges clearly in the intraband excitation, while the intensity of the interband excitation is concentrated around 2 eV near the zone center. The experimental results are consistent with theoretical calculation of the RIXS spectra based on the Hubbard model.

Journal Articles

Electronic excitations in hole-doped La$$_{1-x}$$Sr$$_{x}$$MnO$$_{3}$$ studied by resonant inelastic X-ray scattering

Ishii, Kenji; Inami, Toshiya; Owada, Kenji; Kuzushita, Kaori; Mizuki, Junichiro; Murakami, Yoichi; Ishihara, Sumio*; Endo, Yasuo*; Maekawa, Sadamichi*; Hirota, Kazuma*; et al.

Journal of Physics and Chemistry of Solids, 66(12), p.2157 - 2162, 2005/12

 Times Cited Count:0 Percentile:0(Chemistry, Multidisciplinary)

We have studied electronic excitations of hole-doped manganese oxides La$$_{1-x}$$Sr$$_x$$MnO$$_3$$ ($$x=0.2$$ and $$0.4$$) by resonant inelastic X-ray scattering at Mn K absorption edge. We observed in the excitation spectra that the Mott gap of La$$_{0.6}$$Sr$$_{0.4}$$MnO$$_{3}$$ was filled by hole-doping. In La$$_{0.8}$$Sr$$_{0.2}$$MnO$$_{3}$$, which shows a metal-insulator transition, we found that temperature dependence of scattering intensity is different between two scattering vectors. It may reflects a anisotropic electronic structure which originates from the orbital degrees of freedom in manganese oxides.

Journal Articles

Momentum dependence of charge excitations in the electron-doped superconductor Nd$$_{1.85}$$Ce$$_{0.15}$$CuO$$_4$$; A Resonant inelastic X-ray scattering study

Ishii, Kenji; Tsutsui, Kenji*; Endo, Yasuo*; Toyama, Takami*; Maekawa, Sadamichi*; Hoesch, M.; Kuzushita, Kaori; Tsubota, Masami; Inami, Toshiya; Mizuki, Junichiro; et al.

Physical Review Letters, 94(20), p.207003_1 - 207003_4, 2005/05

 Times Cited Count:72 Percentile:89.21(Physics, Multidisciplinary)

We report a resonant inelastic X-ray scattering (RIXS) study of charge excitations in the electron-doped high-$$T_{c}$$ superconductor Nd$$_{1.85}$$Ce$$_{0.15}$$CuO$$_4$$. The intraband and interband excitations across the Fermi energy are separated for the first time by tuning the experimental conditions properly to measure charge excitations at low energy. A dispersion relation with $${mathbf q}$$-dependent width emerges clearly in the intraband excitation, while the intensity of the interband excitation is concentrated around 2 eV near the zone center. The experimental results are consistent with theoretical calculation of the RIXS spectra based on the Hubbard model.

Journal Articles

Mott gap excitations in twin-free YBa$$_2$$Cu$$_3$$O$$_{7-delta}$$ ($$T_{c}$$ = 93 K) studied by resonant inelastic X-ray scattering

Ishii, Kenji; Tsutsui, Kenji*; Endo, Yasuo*; Toyama, Takami*; Kuzushita, Kaori; Inami, Toshiya; Owada, Kenji; Maekawa, Sadamichi*; Masui, Takahiko*; Tajima, Setsuko*; et al.

Physical Review Letters, 94(18), p.187002_1 - 187002_4, 2005/05

 Times Cited Count:40 Percentile:80.93(Physics, Multidisciplinary)

Mott gap excitations in the optimally doped high-$$T_{c}$$ superconductor YBa$$_2$$Cu$$_3$$O$$_{7-delta}$$ ($$T_{c}$$ = 93 K) have been studied by the resonant inelastic X-ray scattering method. Anisotropic spectra in the $$ab$$-plane are observed in a twin-free crystal. The excitation from the one-dimensional CuO chain is enhanced at 2 eV near the zone boundary of the $$b^{*}$$ direction, while the excitation from the CuO$$_2$$ plane is broad at 1.5-4 eV and almost independent of the momentum transfer. Theoretical calculation based on the one-dimensional and two-dimensional Hubbard model reproduces the observed spectra when different values of the on-site Coulomb energy are assumed. The Mott gap of the CuO chain site is found to be much smaller than that of the CuO$$_2$$ plane site.

Journal Articles

Resonant inelastic X-ray scattering study of the hole-doped manganites La$$_{1-x}$$Sr$$_x$$MnO$$_3$$ ($$x=0.2$$, $$0.4$$)

Ishii, Kenji; Inami, Toshiya; Owada, Kenji; Kuzushita, Kaori; Mizuki, Junichiro; Murakami, Yoichi; Ishihara, Sumio*; Endo, Yasuo*; Maekawa, Sadamichi*; Hirota, Kazuma*; et al.

Physical Review B, 70(22), p.224437_1 - 224437_6, 2004/12

 Times Cited Count:19 Percentile:64.32(Materials Science, Multidisciplinary)

Electronic excitations in the hole doped manganese oxides (La$$_{1-x}$$Sr$$_x$$MnO$$_3$$, $$x=0.2$$ and $$0.4$$) have been elucidated by using the resonant inelastic X-ray scattering (RIXS) method. A doping effect in the strongly correlated electron systems has been observed for the first time. The scattering spectra show that a salient peak appears in low energies indicating the persistence of the Mott gap. At the same time, the energy gap is partly filled by doping holes and the spectral weight energy shifts toward lower energies. The excitation spectra show little change in the momentum space as is in undoped LaMnO$$_3$$. On the other hand, the scattering intensities in the low energy excitations of $$x=0.2$$ are anisotropic in temperature dependence, which indicates an anisotropy of magnetic interaction and underlying effect of the orbital.

Journal Articles

Parallel computation of large-scale eigenvalue problems of strongly correlated electrons on the earth simulator

Yamada, Susumu; Machida, Masahiko; Imamura, Toshiyuki*

Joho Shori Gakkai Rombunshi; Komputeingu Shisutemu (Internet), 45(SIG6(ACS6)), p.161 - 170, 2004/05

no abstracts in English

Journal Articles

Parallel computation of large-scale eigenvalue problems of strongly correlated electrons on the earth simulator

Yamada, Susumu; Machida, Masahiko; Imamura, Toshiyuki*

Hai Pafomansu Komputingu To Keisan Kagaku Shimpojium (HPCS 2004) Rombunshu, p.103 - 110, 2004/01

no abstracts in English

Journal Articles

Liquid-He-free 10-T superconducting magnet for neutron scattering

Katano, Susumu; Minakawa, Nobuaki; Metoki, Naoto; Osakabe, Toyotaka; Suzuki, Junichi; Koike, Yoshihiro; Ishii, Yoshinobu

Applied Physics A, 74(Suppl.1), p.S270 - S272, 2002/12

 Times Cited Count:14 Percentile:50.42(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Single crystal growth and magnetic and electrical properties of an antiferromagnet UCr$$_2$$Si$$_2$$

Matsuda, Tatsuma; Haga, Yoshinori; Tokiwa, Yoshifumi; Yamamoto, Etsuji; Ikeda, Shugo; Okubo, Tomoyuki*; Yamada, Mineko*; Nakamura, Akio; Onuki, Yoshichika

Journal of Nuclear Science and Technology, 39(Suppl.3), p.225 - 228, 2002/11

no abstracts in English

Journal Articles

Probing bulk states of correlated electron systems by high-resolution resonance photoemission

Sekiyama, Akira*; Iwasaki, T.*; Matsuda, K.*; Saito, Yuji; Onuki, Yoshichika*; Suga, Shigemasa*

Nature, 403(6768), p.396 - 398, 2000/01

 Times Cited Count:255 Percentile:98.93(Multidisciplinary Sciences)

no abstracts in English

JAEA Reports

Progress report on neutron scattering research; April 1,1996 - March 31, 1997

Ishii, Yoshinobu; Suzuki, Junichi; Fujiwara, Satoru

JAERI-Review 97-012, 107 Pages, 1997/10

JAERI-Review-97-012.pdf:4.77MB

no abstracts in English

Oral presentation

Development of technique for simultaneous measurement of single-crystal neutron diffraction and electrical resistivity under high pressure

Osakabe, Toyotaka; Kato, Yoshihiro*; Honmoto, Satoru*; Kuwahara, Keitaro*

no journal, , 

no abstracts in English

Oral presentation

Oral presentation

Development of technique for simultaneous measurements of single-crystal neutron diffraction and electrical resistivity under high pressure

Osakabe, Toyotaka; Kuwahara, Keitaro*; Honmoto, Satoru*; Kato, Yoshihiro*

no journal, , 

no abstracts in English

Oral presentation

Phonon modes of $$beta^{prime}$$-(BEDT-TTF)$$_2$$ICl$$_2$$ coupled with charge and spin studied by inelastic neutron scattering

Kawamura, Seiko; Matsuura, Masato*; Iguchi, Satoshi*; Sasaki, Takahiko*; Taniguchi, Hiromi*; Kubota, Aiko*; Sato, Kazuhiko*; Inamura, Yasuhiro; Kikuchi, Tatsuya*; Nakajima, Kenji

no journal, , 

$$beta^{prime}$$-(BEDT-TTF)$$_2$$ICl$$_2$$ is an organic dimer-Mott insulator which exhibits a glassy ferroelectric state below $$T_c$$ = 62K and an antiferromagnetic order below $$T_{rm N}$$ = 22K. It is expected in such molecule-based materials that low-energy phonon modes lie in the energy region of charge and spin, and then the lattice is expected to couple with charge and spin degrees of freedom. To observe such phonon modes in this system, we have performed inelastic neutron scattering study using a chopper spectrometer AMATERAS installed at J-PARC MLF. The system shows the lowest-energy optical phonon mode at $$E$$ = 4.2 meV. which is significantly related to the charge degree of freedom. Analyzing the data more in detail, the intensity of the 4.2 meV-mode monotonically increases with lowering temperature toward $$T_c$$, becomes constant below $$T_c$$ and drastically increases below $$T_{rm N}$$. The behavior of the optical phonons at some representative $$Q$$ positions are reported.

Oral presentation

Large downward renormalization of spin excitation energies in Ba$$_{0.75}$$K$$_{0.25}$$Fe$$_{2}$$As$$_{2}$$ due to electron correlation effects

Murai, Naoki; Kajimoto, Ryoichi; Suzuki, Katsuhiro*; Nakajima, Masamichi*; Ikeda, Hiroaki*; Ideta, Shinichiro*; Tanaka, Kiyohisa*

no journal, , 

We report inelastic neutron scattering (INS) study of hole-doped iron-based superconductor Ba$$_{1-x}$$K$$_{x}$$Fe$$_{2}$$As$$_{2}$$ (x = 0.25). The INS data show a spin-wave-like dispersive feature, with a zone boundary energy of 200 meV. A random phase approximation (RPA) treatment of the dynamical spin susceptibility, incorporating the band renormalization factor of 3 derived from angle-resolved photoemission spectroscopy (ARPES) measurements on the same sample, provides a reasonable description of the observed spin excitations. This analysis shows that the Fe-3d bandwidth narrowing due to electron correlation is directly reflected in the spin excitation energy scale. We will discuss the current state of our analysis relating the magnetic response to the underlying electronic structure of the materials.

Oral presentation

Ordered phases in URhSn; Sn-NMR study

Tokunaga, Yo; Shimizu, Yusei*; Sakai, Hironori; Kambe, Shinsaku; Maurya, A.*; Honda, Fuminori*; Nakamura, Ai*; Li, D.*; Homma, Yoshiya*; Aoki, Dai*

no journal, , 

no abstracts in English

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