| Project/Area Number |
18310073
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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 |
Nanostructural science
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| Research Institution | High Energy Accelerator Research Organization |
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Principal Investigator |
SAWA Hiroshi High Energy Accelerator Research Organization, Institute of Materials Structure Science, Professor (50215901)
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| Project Period (FY) |
2006 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥16,640,000 (Direct Cost: ¥14,900,000、Indirect Cost: ¥1,740,000)
Fiscal Year 2007: ¥7,540,000 (Direct Cost: ¥5,800,000、Indirect Cost: ¥1,740,000)
Fiscal Year 2006: ¥9,100,000 (Direct Cost: ¥9,100,000)
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| Keywords | Synchrotron Radiation X-ray / Single Crystal Structure Analysis / Charge Density Analysis / Molecular Conductor / Charge Ordering / Wigner Crystallization / Charge Density Wave / 雷荷秩序 |
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| Research Abstract |
The Synchrotron Radiation (SR) X-ray is finding increasing use in the study of material science. In this project, we utilized the SR X-ray diffraction methods for the determination of the electronic state in the novel molecular crystals.
Rarefied electron gas system at high temperature is homogeneous due to the large kinetic energy compared to the Coulomb repulsion among electrons. At extreme low temperatures, the system will tend to condense and make uneven lumps, as theoretically predicted in the early 1930's. Since these lumps carry a negative charge, they form a structure where they try to avoid each other in the spatial positioning. We call this phenomenon the Wigner crystallization. A molecular conductor (DI-DCNQI)_2Ag is insulating even at room temperature. Below 220 K, Hiraki and Kanoda suggested that the 4k_F Wigner crystal type of charge order (CO) on DCNQI molecules by NMR technique. This CO ground state was theoretically predicted by Seo, et. al. It is very interesting whether (or how) the electron crystal is stable in the real solid. Single crystal x-ray diffraction measurements using SR were performed at PF, KEK. According to the result of the structural analysis, two-fold structure in ground state consists of not only charge ordering columns but also monotonic charge dimerized columns caused by geometrical frustration among DCNQI columns. In spite of these complicated order parameters, this charge ordered structure is regarded as a Wigner crystal caused by inter-column Coulomb repulsion. This is a first direct observation of the 3D electron crystal. Furthermore, we investigated the electronic state in several molecular materials during the term of project.
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