| Project/Area Number |
62460027
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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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 | The University of Tokyo |
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Principal Investigator |
KAGOSHIMA Seiichi University of Tokyo, College of Arts and Sciences, Professor, 教養学部, 教授 (30114432)
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| Co-Investigator(Kenkyū-buntansha) |
SAITO Gunzi Kyoto University, Faculty of Science, Professor, 理学部 (40132724)
MORI Nobuo University of Tokyo, Institute for Solid State Physics, Professor, 物性研究所, 教授 (40000848)
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| Project Period (FY) |
1987 – 1989
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| Project Status |
Completed (Fiscal Year 1989)
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| Budget Amount *help |
¥8,200,000 (Direct Cost: ¥8,200,000)
Fiscal Year 1989: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1988: ¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1987: ¥5,400,000 (Direct Cost: ¥5,400,000)
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| Keywords | Organic Superconductivity / Structural Change / X-ray Diffraction / High-Pressure Measurements / X線回折 |
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| Research Abstract |
It is characteristic of organic conductors and superconductors that they undergo various types of structural changes which affects electronic properties remarkably. The purpose of the present study is to investigate electronic properties such as the superconductivity from structural points of view through direct observation of structural changes by x-ray diffraction and scattering of single crystals under pressure at low temperature.
In order to observe weak scattering x-rays from organic single crystals at low temperature, we designed a diamond anvil high-pressure cell of special type and a goniometer having a unique structure. We succeeded to obtain high- pressures as high as 5 kbar at 10K in a relatively large sample space of 0,25mm^3. X-ray with diffraction angles of <plus-minus>20ﾟ could be observed without the geometrical restriction of the pressure cell.
We measured x-rays satellite reflections from the superstructure of the organic superconductor bate-(BEDT-TTF)_2I_3 using the above apparatuses.
The followings are the results we obtained: (1) We verified experimentally the speculation that the superstructure is present in the low pressure range below the critical pressure 0.4kbar. (2) We found, however, a decrease in the magnitude of the wave vector below about 110K describing the superstructure.
(3) The changing speed of the wave vector decreases with decreasing pressure.
At ambient, pressure the change needs 40 h to complete. (4) Samples after the wave-vector change have the superconducting critical temperature of 2K, which is obviously higher than that, 1-1.5K, without the change.
Thus we found a correlation between the wave-vector of the superstructure and the superconducting critical temperature. We will investigate what is brought about microscopically by the wave-vector change and what roles it plays in the superconductivity.
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