| Project/Area Number |
16340099
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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 |
Condensed matter physics II
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| Research Institution | The University of Tokyo |
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Principal Investigator |
SAKAKIBARA Toshiro The University of Tokyo, Institute For Solid State Physics, Professor, 物性研究所, 教授 (70162287)
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| Co-Investigator(Kenkyū-buntansha) |
TAYAMA Takashi The University of Tokyo, Institute For Solid State Physics, Research Associate, 物性研究所, 助手 (20334344)
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| Project Period (FY) |
2004 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥15,500,000 (Direct Cost: ¥15,500,000)
Fiscal Year 2006: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 2005: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 2004: ¥11,100,000 (Direct Cost: ¥11,100,000)
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| Keywords | Anisotropic superconductors / Nodal structures / Angle-resolved specific heat measurements / Paramagnetic effect / Skutterudite compounds / anisotropic s-wave superconductor / d-wave superconductor / スカラー型秩序 / 磁化異方性 / 角度分解磁化測定 / ギャップ異方性 / 超伝導混合状態 / 角度分解比熱測定 / スピンアイス化合物 / 強磁性転移 / 第三近接相互作用 / 異方的超伝導体 / ギャップ対称性 / 比熱測定 / 反強四重極転移 / スピンアイス / 気相-液相転移 / 磁気熱量効果 / エントロピー変化 |
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| Research Abstract |
Field-orientation dependent specific heat C(H,θ) measurement is a powerful tool to probe the nodal structure of unconventional superconductors. The principle of the measurement is based on the theoretical prediction that the zero energy density of states induced in the vortex state vary as a function of the angle between the field and the nodal directions. In this project, we have examined the nodal structure of various anisotropic f electron superconductors CeRu_2, PrOs_4Sb_<12> and URu_2Si_2, which are summarized as follows.
1. For CeRu_2, clear fourfold angular oscillation with maxima (minima) along [100] ([110]) directions have been observed. The relative amplitude of the oscillation is a strongly varying function of H and T, and vanishes below 〜0.5 T and 0.3 K. This behavior indicates the presence of a minimum gap of order 〜1 K along the [110] directions, in accordance with the anisotropic s-wave scenario of this system.
2. In PrOs_4Sb_<12>, C(H,θ) exhibits the minima (maxima) along [100] ([111]) in the whole field range below Hc2, indicating a deep minima in the gap amplitude along [100]. The relative oscillation amplitude, however, tends to diminish for H << Hc2, suggesting that the gap is fully opened. No evidence for a symmetry change is observed in the superconducting state.
3. C(H,θ) of URu_2Si_2 shows no angular dependence for H rotated in the basal plane, indicating that the nodal structures have rotational symmetry with respect to the tetragonal c axis. A marked anisotropy is found in C(H) as a function of H/Hc2 suggesting that the gap nodes are rather localized near the c directions. Pauli paramagnetic depairing effect is evidenced in the high field behavior of C(H), indicating d-wave superconductivity.
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