| Project/Area Number |
16340112
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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 | Osaka University (2007)
Central Research Institute of Electric Power Industry (2004-2006) |
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Principal Investigator |
ANDO Yoichi Osaka University, Osaka University, Institute of Scientific and Industrial Research, Professor (90371286)
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| Co-Investigator(Kenkyū-buntansha) |
KOMIYA Seiki (財)電力中央研究所, Central Research Institute of Electric Power Industry, Materials Science Research Laboratory, Research Scientist (80371293)
SEGAWA Kouji (財)電力中央研究所, Central Research Institute of Electric Power Industry, Materials Science Research Laboratory, Research Scientist (20371297)
ONO Shimpei (財)電力中央研究所, Central Research Institute of Electric Power Industry, Materials Science Research Laboratory, Research Scientist (30371298)
孫 学峰 (財)電力中央研究所, 材料科学研究所, 特別契約研究員 (60415883)
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| Project Period (FY) |
2004 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥17,340,000 (Direct Cost: ¥16,200,000、Indirect Cost: ¥1,140,000)
Fiscal Year 2007: ¥4,940,000 (Direct Cost: ¥3,800,000、Indirect Cost: ¥1,140,000)
Fiscal Year 2006: ¥3,800,000 (Direct Cost: ¥3,800,000)
Fiscal Year 2005: ¥4,200,000 (Direct Cost: ¥4,200,000)
Fiscal Year 2004: ¥4,400,000 (Direct Cost: ¥4,400,000)
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| Keywords | High-Tc Superconductor / Self-Organization / Transport Properties / High-Quality Single Crystals / Charge Stripes / Fermi Arc / Thermal Conductivity / Hall Coefficient / 擬ギャップ / 磁場誘起絶縁体状態 / 電荷移動励起 / 電子ドープ / スピン励起 / 磁気抵抗 / チェッカーボード秩序 |
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| Research Abstract |
It is recognized that some sort of electron self-organization occurs in high-Tc cuprate superconductors due to strong electron correlations. Also, it seems likely that in cuprates the electron self-organization phenomena lie behind their peculiar electronic states such as unusual insulating normal state under high magnetic fields or intrinsic inhomogeneity of the superconducting gap. This project has clarified various aspects of the electron self-organization phenomena in cuprates through experiments using high-quality single crystals, in particular their transport properties measurements under extreme conditions. Principal results are the following:
1. We discovered the existence of "magic doping fractions" for charge ordering in La_2-X_Sr_xCuO_4, and showed that a checkerboard model consistently explains the observed fractions.
2. Extensive measurements of ultra-low-temperature thermal conductivity of YBa_2Cu_3O_y, La_2-x_Sr-xCuO_4, and Bi_2Sr_2CaCu_xO_<8+δ> revealed a breakdown of the "universal thermal conductivity", which is generically expected for d-wave BCS superconductors. This breakdown is apparently related to the peculiar superconducting gap inhomogeneity in cuprates.
3. Through the ultra-low-temperature measurements of transport properties of nonsuperconducting YBa_2Cu_3O_y, where a self-organized resistivity anisotropy is known to exist, we elucidated that the electron self-organized state is inherently insulating when it is nonsuperconducting. Moreover, we found that this insulating state is characterized by the peculiar log(1/T) resistivity divergence.
4. We elucidated that the charge transfer energy in the CuO_2 plane can be obtained from the temperature dependence of the Hall coefficient measured up to 1000 K. Furthermore, we showed that the Hall coefficient data can be used for disentangling the phase-separated nature of La_2-x_Sr_xCuO_4 in the superconducting doping regime.
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