| Project/Area Number |
18K03542
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
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| Research Institution | Kyushu Institute of Technology |
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Principal Investigator |
Watanabe Shinji 九州工業大学, 大学院工学研究院, 准教授 (40334346)
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| Project Period (FY) |
2018-04-01 – 2021-03-31
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| Project Status |
Completed (Fiscal Year 2020)
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| Budget Amount *help |
¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
Fiscal Year 2020: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2019: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2018: ¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000)
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| Keywords | グリュナイゼン係数 / 比熱 / 熱膨張係数 / 臨界体積効果 / 磁気体積効果 / 価数量子臨界現象 / 準結晶 / 近似結晶 / 超音波応答 / 弾性定数 / 臨界価数ゆらぎ / SmS / 絶縁体-半金属相転移 / black-golden転移 / エキシトン / グリュナイゼンパラメーター / 量子臨界現象 / 磁気量子臨界点 / SCR理論 / 量子臨界準結晶 / 電子相関 |
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| Outline of Final Research Achievements |
The theoretical framework to calculate the specific heat, the thermal-expansion coefficient, and the Gruneisen parameter due to critical valence fluctuations diverging at the quantum critical point of the valence transition is constructed. By applying this method to the quasicrystal Yb15Al34Au51, the measured temperature dependences of the specific heat, the thermal-expansion coefficient, and the Gruneisen parameter are shown to be well explained. Non-divergent Gruneisen parameter in the quantum-critical quasicrystal Yb15Al34Au51 is shown to be ascribed to the robust criticality against pressure in this material. In the odd-parity crystalline-electric-field arising from the lack of the local inversion symmetry at the Yb site in β-YbAlB4, fluctuations of the odd-parity multipole are shown to be enhanced divergently by the inter-orbital Coulomb repulsion. The theory of the magneto-volume effect is formulated.
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| Academic Significance and Societal Importance of the Research Achievements |
量子臨界点ではグリュナイゼン係数は絶対零度で必ず発散するとこれまで信じられてきたが、圧力に対してrobustな量子臨界性を示す物質では、一般にグリュナイゼン係数は絶対零度で発散しないことを理論的に示した。これは既存概念を覆す新しい概念であり、その学術的意義は大きい。圧力に対してrobustな量子臨界性を示す準結晶Yb15Al34Au51と、特定の圧力でのみそれと共通の量子臨界性を示す近似結晶Yb14Al35Au51でグリュナイゼン係数の振る舞いに違いが出ることを明らかにした本研究の成果は、電子間の局所相互作用によって結晶の幾何学的構造特有の量子現象が生じることを示した学術的意義がある。
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