2010 Fiscal Year Final Research Report
Origin of non-superconducting phase by which the superconducting phase were divided.
| Project/Area Number |
20540354
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Condensed matter physics II
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| Research Institution | Nagoya University |
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Principal Investigator |
KOBAYASHI Yoshiaki Nagoya University, 理学研究科, 准教授 (60262846)
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| Co-Investigator(Kenkyū-buntansha) |
SATO Masatoshi 名古屋大学, 大学院・理学研究科, 名誉教授 (40092225)
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| Project Period (FY) |
2008 – 2010
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| Keywords | 超伝導 / 水和コバルト酸化物 / 核磁気緩和率 / ナイトシフト / 電子比熱係数 / 磁気励起 / 鉄砒素系超伝導体 |
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| Research Abstract |
The superconductivity of the layered cobalt oxides appears in the phase diagram of T-v_Q (or -the lattice parameter c), where the v_Q is Co nuclear electronic quadrupole resonance frequency. In this phase diagram, the non-superconducting (SC) phase appears to divide the SC phase into two regions. To investigate the nature of the non-SC phase, we have measured the T-dependences of various physical properties. The results are consistently understood by the non-SC phase to be not in the magnetic ordered state but in the charge disproportionate state. Although the existences of multi-SC phases and non-SC phase were explained by changing of the relative energy level between a_<1g>-band and e_g'-band of this layered cobalt oxide, we found that the possibility was excluded by those results, for example, the v_Q (or c) dependence of the electronic specific heat coefficient, NMR Knight shift, and the q-dependence of magnetic excitation by neutron scattering measurements. As the non-magnetic impurity does not suppressed the superconductivity, and NMR Knight shift supports the spin-singlet pairing formation, the SC pairing is considered to be formed mainly by electron-phonon interaction, and it is considered that the transition to non-SC phase suppresses the superconductivity though the decreases of the density of states at Fermi level.
Next, we have studied the Fe-based superconductors with ten times as large as T_c for the layered cobalt oxides. Non-magnetic impurity effect on T_c for Fe system was found to be very weak as well as the Co-oxides, indicating that the Fe system is found to give an opportunity to perform comparative studies with the layered cobalt oxides.
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Research Products
(25 results)
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[Presentation] On the superconducting symmetry of Fe pnictides-Impurity effects and results of other measurements-2011
Author(s)
M.Sato, Y.Kobayashi, E.Satomi, S.C.Lee, T.Kawamura, M.Itoh, S.Tatematsu, Y.Yasui, I.Terasaki, K.Kakurai
Organizer
International Workshop on Novel Superconductors and Super Materials 2011 (March 6-8, 2011)
Place of Presentation
National Museum of Emerging Science and Innovation (Miraikan), Tokyo, Japan.
Year and Date
2011-03-06
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[Presentation] On the Magnetic Excitation Spectra of Ba(Fe_<0.9>Co_<0.1>)_2As_2 in the Superconducting State2011
Author(s)
M.Sato, T.Kawamata, Y.Yasui, Y.Kobayashi, T.Moyoshi, K.Motoya, K.Kakurai
Organizer
The International Workshop on Neutron Applications on Strongly Correlated Electron Systems 2011(February 23-25, 2011)
Place of Presentation
Quantum Beam Research Center (IQBRC), Tokai, Ibaraki, Japan.
Year and Date
2011-02-23
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[Presentation] Various Kinds of Studies on the Superconducting Symmetry of Fe-As Systems2009
Author(s)
M.Sato, T.Moyoshi, S.C.Lee, S.Takahashi, Y.Yasui, Y.Kobayashi, K.Kakurai
Organizer
International Workshop, Physics on Transition Metal Based Superocnductors (ICC-IMR Workshop, June 24-26, 2009)
Place of Presentation
IMR, Tohoku University, Sendai Japan.
Year and Date
2009-06-24
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[Presentation] Studies on the Superconducting Symmetry of LaFe_<1-y>Co_yAsO_<1-x>F_x by transport, NMR and Neutron Measurements2009
Author(s)
M.Sato, Y.Kobayashi, S.C. Lee, H.Takahashi, T.Moyoshi, Y.Yasui, S.Tatematsu
Organizer
International Workshop on the Search for New Superconductors-Frontier and Future-(May 12-16, 2009)
Place of Presentation
Shonan Village Center, Hayama-cho, Kanagawa, Japan.
Year and Date
2009-05-12
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[Presentation] Neutron scattering studies of Na_xCoO_2.yD_2O2008
Author(s)
T.Moyoshi, Y.Yasui, Y.Kobayashi, M.Sato, K.Kakurai
Organizer
The International symposium on Anomalous Quantum Materials 2008 and the 7th Asia-Paciffic Workshop (Nov. 7-10, 2008)
Place of Presentation
Yasuda Auditorium, Univ.of Univ.of Tokyo, Tokyo, Japan.
Year and Date
2008-11-08
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