| Project/Area Number |
16340101
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | The University of Tokyo |
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Principal Investigator |
HIROI Zenji The University of Tokyo, The Institute for Solid State Physics, Professor, 物性研究所, 教授 (30192719)
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| Co-Investigator(Kenkyū-buntansha) |
YAMAURA Jun-ichi The University of Tokyo, The Institute for Solid State Physics, Research Associate, 物性研究所, 助手 (80292762)
村岡 祐治 東京大学, 物性研究所, 助手 (10323635)
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| Project Period (FY) |
2004 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥15,500,000 (Direct Cost: ¥15,500,000)
Fiscal Year 2006: ¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 2005: ¥4,300,000 (Direct Cost: ¥4,300,000)
Fiscal Year 2004: ¥8,000,000 (Direct Cost: ¥8,000,000)
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| Keywords | pyrochlore oxide / superconductivity / rattling / transition metal oxide / frustration / strongly correlated electron system / 物質探索 |
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| Research Abstract |
The study of non-Cu-based oxide superconductors has been extended during the last decade, aiming at understanding the role of electron correlations in the mechanism of superconductivity or searching for a novel pairing mechanism, hopefully to reach a higher Tc. An interesting example recently found is a family of pyrochlore oxide superconductors. The first discovered is a-pyrochlore rhenate Cd_2Re_2O_7 with T_c = 1.0 K and the second β-pyrochlore osmate AOs_2O_6 with T_c = 3.3, 6.3, and 9.6 K for A = Cs, Rb, and K, respectively. They crystallize in the cubic pyrochlore structure of space group Fd-3m and commonly possess a 3D skeleton made of ReO_6 or OsO_6 octahedra. The "pyrochlore" sublattice occupied by the transition metal ions is comprised of corner-sharing tetrahedra that are known to be highly frustrating for a localized spin system with antiferromagnetic nearest-neighbor interactions.
Chemical trends of fundamental superconducting parameters and normal-state properties are studied for a family of pyrochlore oxide superconductors. Particularly, the change of T_c from 1.0 K for α-pyrochlore Cd_2Re_2O_7 to 3.3 K (A = Cs), 6.3 K (Rb), and 9.6 K (K) for β-pyrochlore AOs_2O_6 is discussed on the basis of the conventional BCS scheme. Enhanced T_c and anomalous features observed for KOs_2O_6 are ascribed to low-energy phonons probably coming from the rattling of the K cations.
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