| Project/Area Number |
10440100
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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 | University of Tokyo |
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Principal Investigator |
TAKURA Yoshinori University of Tokyo, Department of Applied Physics, Professor, 大学院・工学系研究科, 教授 (30143382)
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| Co-Investigator(Kenkyū-buntansha) |
TAGUCHI Yasujiro University of Tokyo, Department of Applied Physics, Research associate, 大学院・工学系研究科, 助手 (70301132)
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| Project Period (FY) |
1998 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥12,100,000 (Direct Cost: ¥12,100,000)
Fiscal Year 1999: ¥6,100,000 (Direct Cost: ¥6,100,000)
Fiscal Year 1998: ¥6,000,000 (Direct Cost: ¥6,000,000)
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| Keywords | electron-doped high-Tc superconductor / reflectivity spectrum / spin-charge ordering / pseudo-gap structure / charge ordering / electronic phase separation / reducing procedure / suppression of superconductivity / 電子型高温超電導体 / 超電導抑制 / 頂点酸素 / 不純物 / 反強磁性 / 光学伝導度 / 擬ギャップ / 格子異常 |
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| Research Abstract |
We have grown single crystals of Nd_<2-x>Ce_xCuO_<4+y> (x=0, 0.05, 0.1, 0.125, 0.15) by traveling solvent floating zone method and have investigated the temperature dependence of charge and lattice dynamics by the measurements of optical reflectivity spectra. In the as-grown crystals with x=0.05, 0.10, 0.125, we have observed pseudo-gap structure and anomalies in phonon modes at low temperatures which are similar to those observed in non-superconducting sample with x=0.15. This indicates the presence of instability to-ward charge-ordering or electronic phase separation for a broad range of doping levels in this system. The difference from the sample with x=0.15 consists of two points, namely, the increased energy of the pseudo-gap structure and the increased onset temperature of the pseudo-gap with reduced doping-levels.
We have also investigated the reduced crystal with x=0.125 that is in the vicinity of superconducting-nonsuperconducting trasition point. The resistivity shows metallic be-havior, but at low temperature it shows a modest uptern and does not exhibit the super-conductivity. The pseudo-gap structure has been observed to open up at a slightly higher temperature than the resistivity uptern also in this sample. This strongly suggests that the instability that is responsible for the pseudo-gap suppresses the superconductivity in this electron-doped system.
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