2000 Fiscal Year Final Research Report Summary
Direct Observation of Cu-O Plane by STM and Local Pair-breaking Effect on High-T_c Superconductor
| Project/Area Number |
10440095
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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 |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
IDO Masayuki Hokkaido Univ., Graduate School of Sci. Prof., 大学院・理学研究科, 教授 (90111145)
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| Co-Investigator(Kenkyū-buntansha) |
MOMONO Naoki Hokkaido Univ., Graduate School of Sci. Inst., 大学院・理学研究科, 助手 (00261280)
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| Project Period (FY) |
1998 – 2000
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| Keywords | High-Tc Cuprates / STM / CuO plane / Impurity Effect / Pseudo Gap |
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| Research Abstract |
We observed the atomic image of the Cu-O plane of Bi2212 using STM technique. The atomic image of the Cu-O plane for over-doped samples is characterized by cross-striped pattern, implying that the orbit of carriers will result from a strong hybridization of Cu-3d and O-2p orbits. On the other hand, transport and magnetic properties of under-doped (UD) samples indicate that the hybridization of Cu-3d and O-2p orbits will be rather suppressed as doping level is reduced. Therefore, we can expect that the Cu-O atomic image of STM is changed into a simple array of circles in the UD region. However, we could not confirm such a change of the atomic STM image because we failed to prepare UD single crystals of high quality. In the present study, we also studied impurity effects of nonmagnetic Zn- and magnetic Ni-ions on the superconductivity of La214. We found that the superconductivity is locally suppressed over the region where magnetic correlation developed on the Cu 3d-spin network is disturbed by Zn ions. This is the reason why nonmagnetic Zn-ions cause strong local pair-breaking effect compared with magnetic Ni-ions, and implies that the Cu 3d-spin network will play a crucial role in causing the high-Tc superconductivity. It was also found that the pseudo-gap state begins to develop gradually around the mean-field temperature T^* (〜2Δ_O/4.3k_B) and is easily suppressed by doping impurities. The dependence of T^* on impurity concentration is very similar to that of Tc, indicating that the pseudo-gap is closely related with the high-Tc superconductivity, as expected.
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Research Products
(35 results)
