1999 Fiscal Year Final Research Report Summary
Three-body scattering theory for strongly correlated electron system
| Project/Area Number |
10640328
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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 | Gunma University |
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Principal Investigator |
IGARASHI Jun-ichi Gunma University, Faculty of Engineering, Professor, 工学部, 教授 (20127179)
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| Co-Investigator(Kenkyū-buntansha) |
TAKAHASHI Manabu Gunma University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (50250816)
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| Project Period (FY) |
1998 – 1999
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| Keywords | transition-metal oxides / local correlation / photoemission / orbital order / Jahn-Teller distortion / anomalous X-ray scattering / K-absorption edge |
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| Research Abstract |
1. We have calculated the spectra of single-particle excitations on the realistic tight-binding models for LaCuOィイD24ィエD2 and SrィイD22ィエD2CuOィイD22ィエD2ClィイD22ィエD2, which are prototypical antiferromagnetic insulators and the parent compounds of high-Tc superconductors. To deal with strong correlation effects, we have calculated the self-energy for the single-particle Green's function by using the the local three-body scattering approximation, which considers multiple scatterings between three particles excited on the Hartree-Fock (HF) ground state. The present method improved greatly the HF results, leading to good agreement with the photoemission experiments.
2. We have developed a three-body scattering theory to apply to the saturated ferromagnetic state in the two-dimensional Hubbard model. Solving directly the Faddeev equation, we have improved previous variational results.
3. We have proposed an approximate version of the three-body scattering theory as an extension of local approximat
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ion ; the three-body problem is solved by limiting the number of three-body states. Applying this simple extension to the antiferromagnetic state at half-filling in the two-dimensional Hubbard model, we have demonstrated that it gives a reasonable spectral function for the single-particle Green's function in compararison with the results of the exact diagonalization for finite clusters and the quantum Monte Carlo method.
4. We have calculated the resonant X-ray scattering intensity for LaMnOィイD23ィエD2 using the band calculation based on the local density approximation. We have shown that the Jahn-Teller distortion gives rise to large AXS intensities by modifying the 4p states of Mn through the oxygen potential on the neighboring sites. We have also studied the pre-K-edge structure, and have found a two-peak structure with the intensity 〜 1/100 times as small as that of the main peak. This originates from the 4p states of Mn mixing to the 3d states of neighboring Mn sites, and a reflection of the orbital order. Less
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