2003 Fiscal Year Final Research Report Summary
Theoretical Study of Kondo lattices by the 1/d expansion method
| Project/Area Number |
13640342
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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 |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | Hokkaido University |
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Principal Investigator |
OHKAWA Fusayoshi Hokkaido Uiuveisity, Graduate School of Sci., Piofessor, 大学院・理学研究科, 教授 (00107442)
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| Project Period (FY) |
2001 – 2003
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| Keywords | theory of Kondo lattices / 1 / d expansion / high-temperature superconductivity / itinerant-election magnetism / pseudogaps / Mott-Hubbard metal-insulator transition / election-phonon interaction / multiple Q SDW |
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| Research Abstract |
I have developed a theoiy of Kondo lattices for past 16 yeais ; an eaily theoiy of high-temperature superconductivity published in 1987 is also within this theoretical framework. I have applied the theory to the following five issues on strong election correlations : (1)Itinerant-electron ferromagnetism : The supeiexchange interaction can be ferromagnetic for multi-band models, when the Hund coupling is strong enough. The exchange interaction arising from the virtual exchange of pair excitations of quasiparticles can also be ferromagnetic, when the chemical potential is at one of the band edges, in particular, when a sharp peak of the density of states is there. These two exchange interactions are mainly responsible for ferromagnetism in itinerant-election systems. (2)Magnetic structures of itinerant-electron antiferromagnets : When there are equivalent nesting vectors, multiple Q spin density wave (SDW) states can be stabilized ; magnetizations with different Q should be orthogonal to each other for double or triple Q SDW. (3)Pseudogaps in normal states of high-temperature superconductors : Anisotropic pseudogaps can appear because of large life-time widths of quasiparticles, which are mainly caused by dγ-wave superconducting fluctuations. (4)Election-phonon interaction in high-temperature superconductors : I have proposed a novel electron-phonon interaction arising from the modulation of the superexchange interaction by phonons. This election-phonon interaction can explain kinks in the quasiparticle dispersion and the softening of phonons m cuprates. (5)Mott-Hubbard metal-insulator crossover in disordered Kondo lattices : The asymmetry of the crossovei between hole-doped and electron-doped cuprates can be explained by a theory of disordered Kondo lattices, if disorder of hole-doped cuprates is relatively larger than that of election-doped cuprates.
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