| Project/Area Number |
61460028
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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 | University of Tokyo |
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Principal Investigator |
SHUN-ICHI Kobayashi Faculty of Science, University of Tokyo, Professor, 理学部, 教授 (90029471)
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| Co-Investigator(Kenkyū-buntansha) |
FUMIO Komori Faculty of Science, University of Tokyo, Assistant, 理学部, 助手 (60170388)
YOUITI Ootuka Cryogenic Center, University of Tokyo, Associate Professor, 低温センター, 助教授 (50126009)
SEIICHIRO Ikehata Faculty of Science, University of Tokyo, Associate Professor, 理学部, 助教授 (30107685)
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| Project Period (FY) |
1986 – 1988
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| Project Status |
Completed (Fiscal Year 1988)
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| Budget Amount *help |
¥6,100,000 (Direct Cost: ¥6,100,000)
Fiscal Year 1988: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1987: ¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 1986: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Keywords | anderson transition / metal-insulator transition / 臨界指数 / 金属・非金属転移 / アンダーソン局在 / スピン帯磁率の異常 / 不純物半導体 / 微粒子 / 積層膜 / 超伝導 |
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| Research Abstract |
The wave function of conduction electrons in metals localizes when the randomness of the potential exceeds some critical value. This phenomenon, called the Anderson transition, has been studied for long time. Since the new scaling theory was presented in 1979, extensive studies were done mainly in the weakly localized regime, and the almost complete understanding has been established. This project aims to study the more strongly localized regime including the metal-insulator transition.
We investigated three systems; the doped semiconductors, the packed metallic small particles and the persistent photoconductors.
For the first system, the magnetic susceptibility of Si:P and Ge:Sb were measured through the transition, and it was confirmed that there is no magnetic instability, which some theories predicted, at the transition.
We used packed small particles of copper, bismuth and aluminium of which the surface was lightly oxidized for the second system. From the results of copper based samples, we found that the critical index is unity even in the presence of the spin scattering and the spin-orbit interaction. The conditions for the appearance of normal-metallic phase between the superconducting and insulating phases were studied in Al based samples.
In the third system of AlGaAs, the electron concentration was finely swept across the transition. The conductivity and the dielectric constant were measured. The index for conductivity was unity.
We compared these results with the scaling theories and found that there are a number of disagreements. We need further development in the theories to understand the physics of the transition.
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