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Journal Articles

Experimental determination of the topological phase diagram in Cerium monopnictides

Kuroda, Kenta*; Ochi, Masayuki*; Suzuki, Hiroyuki*; Hirayama, Motoaki*; Nakayama, Mitsuhiro*; Noguchi, Ryo*; Bareille, C.*; Akebi, Shuntaro*; Kunisada, So*; Muro, Takayuki*; et al.

Physical Review Letters, 120(8), p.086402_1 - 086402_6, 2018/02

 Times Cited Count:42 Percentile:92.13(Physics, Multidisciplinary)

Journal Articles

Momentum-resolved charge excitations in high-$$T$$$$_{rm c}$$ cuprates studied by resonant inelastic X-ray scattering

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:18.18(Chemistry, Multidisciplinary)

Journal Articles

Phonon softening in superconducting diamond

Hoesch, M.*; Fukuda, Tatsuo; Mizuki, Junichiro; Takenouchi, Tomohiro*; Kawarada, Hiroshi*; Sutter, J. P.*; Tsutsui, Satoshi*; Baron, A. Q. R.*; Nagao, Masanori*; Takano, Yoshihiko*

Physical Review B, 75(14), p.140508_1 - 140508_4, 2007/04

 Times Cited Count:35 Percentile:77.53(Materials Science, Multidisciplinary)

We observed phonon dispersions using inelastic X-ray scattering from CVD-grown high quality superconducting ($$T_c$$=4.2 K) boron-doped and non-doped diamonds. By comparing these two, we found almost no change in the acoustic branch along both [111] and [001] directions. On the other hand, strong softening were observed in the optical branch of the boron-doped diamond in both directions: about 2 meV at Brillouin zone boundary and 8 meV at zone center ($$Gamma$$ point). From this result we estimated the electron-phonon coupling factor $$lambda$$=0.33, and this supports theoretical models suggesting a phonon-mediated pairing mechanism via coupling of optical phonon modes to Fermi surfaces around the $$Gamma$$ point.

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

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:70 Percentile:89.23(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.

Oral presentation

Resonant inelastic X-ray scattering in strongly correlated electron systems

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-$$T_c$$ superconductors Nd$$_{2-x}$$Ce$$_x$$CuO$$_4$$ and YBa$$_2$$Cu$$_3$$O$$_{6+x}$$ are presented. In Nd$$_2$$CuO$$_4$$ and YBa$$_2$$Cu$$_3$$O$$_6$$, 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 $$[pi,pi]$$ direction than the $$[pi,0]$$ direction. An intraband excitation in the upper Hubbard band emerges in the spectra of electron-doped Nd$$_{1.85}$$Ce$$_{0.15}$$CuO$$_4$$. As a function of the momentum transfer in the CuO$$_2$$ 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$$_2$$Cu$$_3$$O$$_7$$ 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$$_2$$ plane site.

Oral presentation

Phonon softening in boron doped diamond

Fukuda, Tatsuo; Hoesch, M.*; Takenouchi, Tomohiro*; Sutter, J. P.*; Tsutsui, Satoshi*; Baron, A.*; Nagao, Masanori*; Takano, Yoshihiko*; Kawarada, Hiroshi*; Mizuki, Junichiro

no journal, , 

Diamond is well known for its maximum hardness, large energy gap, high thermal conductivity, and so on. In addition to these, the superconductivity was discovered recently in boron doped (B-doped) diamond, and this was soon confirmed by other groups. We performed inelastic X-ray scattering experiments at BL35XU of SPring-8 to measure phonons in a highly B-doped CVD grown diamond having superconducting transition at $$T_csimeq$$4.2 K. By comparing the experimental results with those from nitrogen doped CVD grown diamond and/or pure diamond, we found that the optical modes are softened especially at around the Brillouin zone center along with a strong broadening, while the acoustic modes do not show both softening and broadening. This confirms the strong electron-phonon coupling in superconducting diamond.

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