| Project/Area Number |
12450003
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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 | The University of Tokyo |
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Principal Investigator |
HANAGURI Tetsuo Graduate School of Frontier Sciences, The University of Tokyo, Professor, 大学院・新領域創成科学研究科, 助教授 (40251326)
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| Co-Investigator(Kenkyū-buntansha) |
MAEDA Atsutaka Graduate School of Frontier Sciences, The University of Tokyo, Associate Professor, 大学院・総合文化研究科, 助教授 (70183605)
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| Project Period (FY) |
2000 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥7,700,000 (Direct Cost: ¥7,700,000)
Fiscal Year 2001: ¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2000: ¥4,100,000 (Direct Cost: ¥4,100,000)
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| Keywords | Flux flow resistivity / Electronic specific heat coefficient / Surface Impedance / Scanning tunneling microscopy / High-T_c superconductors / NbSe_2 / YNi_2B_2C / 電界イオン顕微鏡 / 電荷密度波 / 磁束 / Kramer-Pesch効果 / マイクロ波伝導度 / 走査型トンネル分光 |
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| Research Abstract |
In this study, we examined the electronic states of vortex states of various clean superconductors such as high-T_c cuprates, NbSe_2 and YNi_2B_2C by utilizing the surface impedance measurements, specific heat measurements and scanning tunneling microscopy (STM).
We succeeded in building a surface impedance measurement apparatus which works at very low temperatures down to 0.5K under magnetic fields. By using this apparatus, we measured flux flow resistivity of YBa_2Cu_3O_y and strongly anisotropic s-wave superconductor YNi_2B_2C. From the analysis, we found that the electronic state of vortex core of YBa_2Cu_3O_y is in the so-called "moderately clean" regime and vortex core is somewhat different from classical normal state core. In YNi_2B_2C, flux flow resistivity was almost twice as large as that expected from the conventional Bardeen Stephen model. This result indicates that the energy dissipation in the vortex core is strongly affected by the anisotropy of the superconducting gap.
We also measured the magnetic field H dependence of electronic specific heat coefficients of various NbSe_2 crystals and found that the quasi-particle density of states (QPDOS) deviates from conventional H-linear behavior with increasing sample purity. From measurements on the sample containing columnar defects introduced by heavy ion irradiation, we found that the QPDOS anomaly is brought by quasi particles outside of vortex cores. From the comparative resistivity measurements and STM observations, we conclude that the QPDOS anomaly is strongly correlated with the evolution of charge-density wave which coexists with superconductivity.
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