2018 Fiscal Year Final Research Report
Quantum anomaly and topology in layered ruthenates
| Project/Area Number |
17K14326
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| Research Category |
Grant-in-Aid for Young Scientists (B)
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| Allocation Type | Multi-year Fund |
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| Research Field |
Condensed matter physics II
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| Research Institution | Hokkaido University |
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Principal Investigator |
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| Project Period (FY) |
2017-04-01 – 2019-03-31
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| Keywords | スピン三重項超伝導 / トポロジー / 量子アノマリー / 高温超伝導 |
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| Outline of Final Research Achievements |
We report the observation of a Chern structure in the Bose-insulating phase of Sr2RuO4 nanofilms by employing electric transport. Fractional quantized conductance was observed without an external magnetic field. We found an anomalous induced voltage with temperature and thickness dependence, and the induced voltage exhibited switching behavior when we applied a magnetic field. We suggest that there was fractional magnetic-field-induced electric polarization in the interlayer.
We report the realization of high-temperature superconductivity in Ca2RuO4 nanofilm single crystals. A Ca2RuO4 thin-film exhibits zero resistance and typical Berezinskii-Kosterlitz-Thouless transition behavior where the highest onset temperature 96 K is observed in electric transport measurements. We also found that the induced bias current and the tuned film thickness cause a superconductor-insulator transition.
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| Free Research Field |
低次元電子物性
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| Academic Significance and Societal Importance of the Research Achievements |
近年トポロジ－を切り口とした物性研究が盛んに研究されている．その中でもスピン三重項超伝導・超流動は最も興味深い研究分野の一つである．スピン三重項超伝導微小試料内で実現する量子異常による新奇量子状態を微細加工や測定手法により制御することでトポロジーや双対性、非可換性物理の開拓に繋がる．
これまでルテニウム酸化物における高温超伝導は実験的に報告されておらず、本研究における成果は初めて得られたものである．“室温超伝導の実現”は21世紀物理学への大きな問いかけであり、高温超伝導研究、室温超伝導の探索にナノ技術が加わることでTcを制御する新たな転換となることが期待される．
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