1997 Fiscal Year Final Research Report Summary
Study of electronic phase transitions in composite copper oxides by intercalation
| Project/Area Number |
07455001
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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 |
Applied materials science/Crystal engineering
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| Research Institution | Tohoku University |
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Principal Investigator |
KOIKE Yoji Tohoku University, School of Engineering, professor, 大学院・工学研究科, 教授 (70134038)
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| Co-Investigator(Kenkyū-buntansha) |
KATO Masatsune Tohoku University, School of Engineering, Research Assistant, 大学院・工学研究科, 助手 (50211850)
NOJI Takashi Tohoku University, School of Engineering, Research Assistant, 大学院・工学研究科, 助手 (50180740)
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| Project Period (FY) |
1995 – 1997
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| Keywords | high-Tc superconductvity / intercalation / Bi-based high-Tc superconductor / anisotropy / multilayr / proximity / excess oxygen |
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| Research Abstract |
We have studied changes of the anisotropy (dimensionality), The carrier concentration and the superconducting transition temperature Tc through intercalation of halogen in the Bi-based high-Tc superconductors, in order to obtain some informations on the mechanism of high-Tc superconductivity. The results obtained are as follows.
1.We have found that the experimental results are explained by the multilayr model, where a high-Tc superconductor is regarded as an alternating stack of the CuO_2 layr (superconducting layr) and the so-called block layr (normal layr), taking account of the redistribution of carriers and of the proximity effect. Although the mechanism of the intrinsic superconductivity in the superconducting layrs remains unsettles, the attractive potential between electrons is estimated as ca. 2000 K.This means that the attractive potential is expected to be no longer caused by the phonon-mediated machanism but by another machanism due to a rather high-energy driving force.
2.From the experiment of iodine intercaltion into the Co-substituted Bi2122 phase, we have found that the decrease in Tc through the iodine intercalation is attributed to not only the increase of the hole concentration in the CuO_2 planes but also the decoupling between adjacent blocks of the CuO_2 planes. This result supports the above-mentioned multilayr model.
3.We have succeeded in making the Bi2222 phase superconducting through halogen intercalation. We have concluded that the role of the annealing under high pressures of oxygen in the appearance of superconductivity for the Bi2222 phase is to suppply the CuO_2 planes with enough hole carriers.
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