| Project/Area Number |
16H07447
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| Research Category |
Grant-in-Aid for Research Activity Start-up
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| Allocation Type | Single-year Grants |
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| Research Field |
Condensed matter physics II
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| Research Institution | Okayama University (2017-2019)
Institute of Physical and Chemical Research (2016) |
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Principal Investigator |
Takemori Nayuta 岡山大学, 異分野基礎科学研究所, 特任助教 (10784085)
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| Project Period (FY) |
2016-08-26 – 2019-03-31
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| Project Status |
Completed (Fiscal Year 2019)
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| Budget Amount *help |
¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2017: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2016: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000)
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| Keywords | 超伝導 / 準周期系 / 準結晶 / 強相関電子系 |
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| Outline of Final Research Achievements |
We numerically study the physical properties of quasiperiodic superconductors with the aim of understanding superconductivity in quasicrystals.
Considering the attractive Hubbard model on the Penrose tiling as a simple theoretical model, we calculate stabilities of superconductivity in quasiperiodic system and various basic superconducting properties and find deviations from the universal values of the Bardeen-Cooper-Schrieffer theory. In particular, we find that the jump of the specific heat at the superconducting transition is about 10-20% smaller than that universal value, in consistency with the experimental results obtained for the superconducting Al-Mg-Zn quasicrystalline alloy.
Furthermore, we calculate current-voltage characteristics and find that the current gradually increases with the voltage on the Penrose tiling in contrast to a rapid increase in the periodic system. These distinctions originate from the nontrivial Cooper pairing characteristic to the quasiperiodic system.
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| Academic Significance and Societal Importance of the Research Achievements |
準結晶とは、周期性とは異なる空間秩序を有する物質である。超伝導はいろいろな物質で発見されてきたが、並進対称性のない準結晶で発見された弱結合超伝導状態は周期結晶で知られるBCS超伝導状態と異なる可能性が高い。本研究では、準結晶を特徴づける構造として知られる準周期系で超伝導がどのような特徴を持つのか、という問題を数値シミュレーションを用いて理論的に考察した。その結果、準周期系の弱結合領域の超伝導状態がBCS超伝導とは異なる空間的に広がった(Extended)超伝導であることを示した。また、比熱の跳びが実験値と近い値を示し、実験結果はExtended 超伝導状態と矛盾しないことを明らかにした。
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