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Arai, Yosuke*; Kuroda, Kenta*; Nomoto, Takuya*; Tin, Z. H.*; Sakuragi, Shunsuke*; Bareille, C.*; Akebi, Shuntaro*; Kurokawa, Kifu*; Kinoshita, Yuto*; Zhang, W.-L.*; et al.
Nature Materials, 21(4), p.410 - 415, 2022/04
Times Cited Count:14 Percentile:75.71(Chemistry, Physical)Murai, Naoki; Fukuda, Tatsuo; Nakajima, Masamichi*; Kawamura, Mitsuaki*; Ishikawa, Daisuke*; Tajima, Setsuko*; Baron, A. Q. R.*
Physical Review B, 101(3), p.035126_1 - 035126_6, 2020/01
Times Cited Count:7 Percentile:35.00(Materials Science, Multidisciplinary)We report an inelastic X-ray scattering investigation of phonons in FeSe superconductor. Comparing the experimental phonon dispersion with density functional theory (DFT) calculations in the non-magnetic state, we found a significant disagreement between them. A better overall agreement was obtained by allowing for spin-polarization in DFT calculations, despite the absence of magnetic order in FeSe. This calculation gives a realistic approximation, at DFT level, of the disordered paramagnetic state of FeSe, in which strong spin fluctuations are present.
Murai, Naoki; Fukuda, Tatsuo; Tajima, Setsuko*; Baron, A. Q. R.*
Hoshako, 32(4), p.199 - 208, 2019/07
Phonon spectra of detwinned SrFeAs
crystals, as measured by inelastic X-ray scattering, show clear anisotropy accompanying the magneto-structural transition at 200 K. We model the modesplitting using magnetic DFT calculations, including a phenomenological reduction in force-constant anisotropy that can be attributed to magnetic fluctuations. This serves as a starting point for a general model of phonons in this material applicable to both magnetic and non-magnetic phase.
Murai, Naoki*; Fukuda, Tatsuo; Kobayashi, Tatsuya*; Nakajima, Masamichi*; Uchiyama, Hiroshi*; Ishikawa, Daisuke*; Tsutsui, Satoshi*; Nakamura, Hiroki; Machida, Masahiko; Miyasaka, Shigeki*; et al.
Physical Review B, 93(2), p.020301_1 - 020301_5, 2016/01
Times Cited Count:7 Percentile:31.52(Materials Science, Multidisciplinary)Hirata, Yasuyuki*; Kojima, Kenji*; Uchida, Shinichi*; Ishikado, Motoyuki; Iyo, Akira*; Eisaki, Hiroshi*; Tajima, Setsuko*
Physica C, 470(Suppl.1), p.S44 - S46, 2010/12
Times Cited Count:2 Percentile:11.32(Physics, Applied)Infrared reflectivity spectra of the multilayered HgBaCa
Cu
O
(
= 2, 3, 4, and 5) are measured. Optical plasma modes associated with the Josephson coupling between CuO
planes within a multilayer appear below
in the c-axis component of the reflectivity spectrum. For the bilayer and trilayer compound an optical Josephson plasma mode appears at unprecedentedly high frequency,
700-800 cm
, below
. The plasma frequencies appreciably decrease in four- and five-layer compounds which indicates the suppression of superconducting order in the inner CuO
planes, consistent with the result of NMR experiment.
Ishii, Kenji; Hoesch, M.*; Inami, Toshiya; Kuzushita, Kaori*; Owada, Kenji; Tsubota, Masami; Murakami, Yoichi; Mizuki, Junichiro; Endo, Yasuo; Tsutsui, Kenji*; et al.
Journal of Physics and Chemistry of Solids, 69(12), p.3118 - 3124, 2008/12
Times Cited Count:3 Percentile:17.73(Chemistry, Multidisciplinary)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- superconductor YBa
Cu
O
(
= 93 K) have been studied by the resonant inelastic X-ray scattering method. Anisotropic spectra in the
-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
direction, while the excitation from the CuO
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
plane site.
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:80.30(Physics, Multidisciplinary)Mott gap excitations in the optimally doped high- superconductor YBa
Cu
O
(
= 93 K) have been studied by the resonant inelastic X-ray scattering method. Anisotropic spectra in the
-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
direction, while the excitation from the CuO
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
plane site.
Arai, Yosuke*; Kuroda, Kenta*; Tsutsui, Satoshi*; Hirai, Daigoro*; Katayama, N.*; Nomoto, Takuya*; Shin, S.*; Kubota, Masato; Haga, Yoshinori; Suzuki, Hiroyuki*; et al.
no journal, ,
no abstracts in English
Arai, Yosuke*; Kuroda, Kenta*; Tsutsui, Satoshi*; Hirai, Daigoro*; Katayama, Wago*; Shin, S.*; Kubota, Masato; Nomoto, Takuya*; Suzuki, Hiroyuki*; Miyasaka, Shigeki*; et al.
no journal, ,
no abstracts in English
Murai, Naoki*; Fukuda, Tatsuo; Uchiyama, Hiroshi*; Tsutsui, Satoshi*; Ishikawa, Daisuke*; Kobayashi, Tatsuya*; Nakamura, Hiroki; Machida, Masahiko; Nakajima, Masamichi*; Miyasaka, Shigeki*; et al.
no journal, ,
no abstracts in English
Murai, Naoki; Fukuda, Tatsuo; Kobayashi, Tatsuya*; Nakajima, Masamichi*; Uchiyama, Hiroshi*; Ishikawa, Daisuke*; Tsutsui, Satoshi*; Nakamura, Hiroki; Machida, Masahiko; Miyasaka, Shigeki*; et al.
no journal, ,
We report the first IXS study of single crystals of SrFeAs
that have been detwinned via application of in-plane uniaxial stress. Our results clearly show anisotropy in phonon structure below
=
characterized by mode splitting at tetragonally-equivalent momentum transfers. To the best of our knowledge, this is the first observation of phonon anisotropy in iron-pnictides at finite momentum transfers. We obtain good agreement with our results using calculations that are modified to account for a reduced magnetic moment and fluctuating magnetism. Previous efforts using either non-magnetic calculations or static magnetism tend to either get the dispersion wrong from non-magnetic calculations or strongly over-estimate the phonon mode splitting when static magnetism is included. Our model for the response below
incorporates a phenomenological reduction in force constant anisotropy, by about 65%, that can be attributed to residual fast magnetic fluctuations. Above
, all fluctuations are assumed to be fast and the response becomes the average of the results from the static magnetism. This serves as a starting point for a general model of phonons in iron-pnictides applicable to both non-magnetic and magnetic phases.
Arai, Yosuke*; Kuroda, Kenta*; Nomoto, Takuya*; Hirai, Daigoro*; Katayama, Wago*; Tsutsui, Satoshi*; Tanaka, Hiroaki*; Arita, Masashi*; Shin, S.*; Kubota, Masato; et al.
no journal, ,
no abstracts in English
Arai, Yosuke*; Kuroda, Kenta*; Tsutsui, Satoshi*; Hirai, Daigoro*; Tanaka, Hiroaki*; Yuyang, D.*; Iwata, Takuma*; Katayama, Kazu*; Shin, S.*; Kubota, Masato; et al.
no journal, ,
no abstracts in English
Murai, Naoki; Fukuda, Tatsuo; Nakajima, Masamichi*; Kawamura, Mitsuaki*; Ishikawa, Daisuke*; Tajima, Setsuko*; Baron, A.*
no journal, ,
Ishii, Kenji; Tsutsui, Kenji*; Endo, Yasuo*; Toyama, Takami*; Inami, Toshiya; Owada, Kenji; Kuzushita, Kaori*; Hoesch, M.; Tsubota, Masami; Mizuki, Junichiro; et al.
no journal, ,
Resonant inelastic X-ray scattering studies on high- superconductors Nd
Ce
CuO
and YBa
Cu
O
are presented. In Nd
CuO
and YBa
Cu
O
, which are Mott insulators, an excitation across the Mott gap is observed around 2 eV. The spectral weight of this excitation shifts to higher energy with increasing the momentum transfer and the dispersion of the excitation is larger along the
direction than the
direction. An intraband excitation in the upper Hubbard band emerges in the spectra of electron-doped Nd
Ce
CuO
. As a function of the momentum transfer in the CuO
plane, the excitation shifts to higher energy up to 2-2.5 eV at the zone boundary, accompanied by an increase of the spectral width. On the other hand, excitations from two inequivalent Cu sites in hole-doped YBa
Cu
O
are distinguished by the momentum dependence and the Mott gap of the CuO chain site is found to be much smaller than that of the CuO
plane site.
Murai, Naoki*; Fukuda, Tatsuo; Nakajima, Masamichi*; Kobayashi, Tatsuya*; Uchiyama, Hiroshi*; Tsutsui, Satoshi*; Ishikawa, Daisuke*; Nakamura, Hiroki; Machida, Masahiko; Miyasaka, Shigeki*; et al.
no journal, ,