| Project/Area Number |
60540201
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体物性
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| Research Institution | Nagoya University |
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Principal Investigator |
NAGAOKA Yosuke Nagoya University Professor, 理学部, 教授 (60022539)
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| Co-Investigator(Kenkyū-buntansha) |
MIYAKE Kazumasa Nagoya University Associate Professor, 教養部, 助教授 (90109265)
MATSUURA Tamifusa Nagoya University Associate Professor, 理学部, 助教授 (10022609)
KURODA Yoshihiro Nagoya University Associate Professor, 理学部, 助教授 (60013504)
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| Project Period (FY) |
1985 – 1987
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| Project Status |
Completed (Fiscal Year 1987)
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| Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1987: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1986: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1985: ¥500,000 (Direct Cost: ¥500,000)
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| Keywords | Dense Kondo System / Heavy Electrons / Periodic Anderson Model / Spin Fluctuation / Anisotropic Superconductivity / Local Phonon Modes / 高温超伝導 / 重いフェルミ粒子 / 電子間引力 / 電子格子相互作用 |
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| Research Abstract |
We studied the origin of heavy electrons which are found in Ce- or U-compounds, showed that the heavy-electron behavior can be observed in various systems besides these materials, and investigated their properties, in particular the superconductivity.
1. The origin of heavy electrons
The system of heavy electrons is considered as the dense Kondo system which can be described by the periodic Anderson model. It was studied by the perturbational expansion and the 1/N expansion, N being the degeneracy of localized levels. The relaxation time of conduction electrons, in particular, was calculated in the whole temperature region.
2. Superconductivity of heavy electrons
The mechanism of superconductivity in heavy electrons is the effective attraction mediated by the spin fluctuation. Then the superconducting state is expected to be anisotropic. From this viewpoint, various properties of the superconducting state, including the ultrasonic attenuation, were studied.
3. Heavy electrons due to the interaction with local phonon modes.
It was shown that electrons interacting strongly with local phonon modes with strong anharmonicity behave as heavy electrons. Their properties, in particular superconductivity, were studied.
4. The mechanism of high-T_c superconductivity
In oxide superconductors with high transition temperatures, the electric conduction takes place in the two-dimensional plane consisting of copper and oxigen ions. In the plane strong repulsion acts between electrons in d-levels of copper ions and the conduction band is formed by p-levels of oxigen ions. The systemis considered as the periodic Anderson model in two dimensions. Then the spin fluctuation plays the most important role in the mechanism of superconductivity. Various properties of the system in normal and superconducting states were studied from this viewpoint.
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