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- Kazuhiko Kuroki, Seiichiro Onari, +4 authors Hideo Aoki
- Physical review letters
- 2008

For a newly discovered iron-based high T_{c} superconductor LaFeAsO1-xFx, we have constructed a minimal model, where inclusion of all five Fe d bands is found to be necessary. The random-phase approximation is applied to the model to investigate the origin of superconductivity. We conclude that the multiple spin-fluctuation modes arising from the nestingâ€¦ (More)

- Seiichiro Onari, Hiroshi Kontani
- Physical review letters
- 2009

Based on the five-orbital model, we study the effect of local impurity in iron pnictides, and find that the interband impurity scattering is promoted by the d-orbital degree of freedom. This fact means that the fully gapped sign-reversing s-wave state, which is predicted by spin fluctuation theories, is very fragile against impurities. In the BCS theory,â€¦ (More)

- Hiroshi Kontani, Seiichiro Onari
- Physical review letters
- 2010

In iron pnictides, we find that the moderate electron-phonon interaction due to the Fe-ion oscillation can induce the critical d-orbital fluctuations, without being prohibited by the Coulomb interaction. These fluctuations give rise to the strong pairing interaction for the s-wave superconducting (SC) state without sign reversal (s(++)-wave state), which isâ€¦ (More)

- Seiichiro Onari, Hiroshi Kontani
- Physical review letters
- 2012

We study the mechanism of orbital or spin fluctuations due to multiorbital Coulomb interaction in iron-based superconductors, going beyond the random-phase approximation. For this purpose, we develop a self-consistent vertex correction (VC) method, and find that multiple orbital fluctuations in addition to spin fluctuations are mutually emphasized by theâ€¦ (More)

- Masahisa Tsuchiizu, Yusuke Ohno, Seiichiro Onari, Hiroshi Kontani
- Physical review letters
- 2013

Motivated by the nematic electronic fluid phase in Sr(3)Ru(2)O(7), we develop a combined scheme of the renormalization-group method and the random-phase-approximation-type method, and analyze orbital susceptibilities of the (d(xz), d(yz))-orbital Hubbard model with high accuracy. It is confirmed that the present model exhibits a ferro-orbital instabilityâ€¦ (More)

- Kazuhiko Kuroki, Shuhei Ohkubo, Takumi Nojima, Ryotaro Arita, Seiichiro Onari, Yukio Tanaka
- Physical review letters
- 2007

We analyze the origin of the three-dimensional (3D) magnetism observed in nonhydrated Na-rich Na(x)CoO2 within an itinerant spin picture using a 3D Hubbard model. The origin is identified as the 3D nesting between the inner and outer portions of the Fermi surface, which arise due to the local minimum structure of the a(1g) band at the Gamma-A line. Theâ€¦ (More)

- T. Yoshida, S. Ideta, +32 authors Honda Kontani
- Scientific reports
- 2014

We report peculiar momentum-dependent anisotropy in the superconducting gap observed by angle-resolved photoemission spectroscopy in BaFe2(As(1-x)P(x))2 (x = 0.30, Tc = 30â€…K). Strongly anisotropic gap has been found only in the electron Fermi surface while the gap on the entire hole Fermi surfaces are nearly isotropic. These results are inconsistent withâ€¦ (More)

- Ryotaro Arita, Seiichiro Onari, Kazuhiko Kuroki, Hideo Aoki
- Physical review letters
- 2004

In order to probe the effect of charge fluctuations on triplet pairing, we study the pairing symmetry in the one-band Hubbard model having the off-site Coulomb repulsion (V) on top of the on-site repulsion as a model for the gamma band of Sr2RuO4, a strong candidate for a triplet pairing superconductor. The result, obtained with the dynamical clusterâ€¦ (More)

- Naoyuki Katayama, Seiichiro Onari, Kazuyuki Matsubayashi, Yoshiya Uwatoko, Hiroshi Sawa
- Scientific reports
- 2016

We report the comprehensive studies between synchrotron X-ray diffraction, electrical resistivity and magnetic susceptibility experiments for the iron arsenides Can(n+1)/2(Fe1-xPtx)(2+3n)Ptn(n-1)/2As(n+1)(n+2)/2 for nâ€‰=â€‰2 and 3. Both structures crystallize in the monoclinic space group P21/m (#11) with three-dimensional FeAs structures. The horizontal FeAsâ€¦ (More)

- Seiichiro Onari, Youichi Yamakawa, Hiroshi Kontani
- Physical review letters
- 2014

The isostructural transition in the tetragonal phase with a sizable change in the anion height, is realized in heavily H-doped LaFeAsO and (La,P) codoped CaFe2As2. In these compounds, the superconductivity with higher Tc (40-50 K) is realized near the isostructural transition. To find the origin of the anion-height instability and the role in realizing theâ€¦ (More)