2021 Fiscal Year Final Research Report
Superconductivity of SrTiO3 near a non-magnetic quantum critical point
| Project/Area Number |
19H01844
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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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| Review Section |
Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
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| Research Institution | National Institute of Advanced Industrial Science and Technology |
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Principal Investigator |
Tomioka Yasuhide 国立研究開発法人産業技術総合研究所, エレクトロニクス・製造領域, 上級主任研究員 (60357572)
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| Project Period (FY) |
2019-04-01 – 2022-03-31
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| Keywords | 超伝導 / 強誘電体 / 量子臨界点 / チタン酸ストロンチウム / 酸素同位体置換 |
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| Outline of Final Research Achievements |
Different-type of ferroelectrics, Sr1-yCayTiO3 [TC(FE) = 25 K] and Sr1-yBayTiO3 [TC(FE) = 50 K], show superconductivity by the systematic substitution of Nb5+ for Ti4+ for the electron doping. The two polar metals commonly exhibit a simple superconducting dome with a single convex on top, like Sr1-xLaxTiO3 and SrTi1-xNbxO3. The superconducting transition temperature Tc is enhanced in both polar metals compared with non-polar SrTi1-xNbxO3. Moreover, the maximum Tc reaches 0.75 K, the highest in the families of SrTiO3 ever reported. Interestingly, the Tc enhancement is low in the vicinity of the ferroelectric quantum critical point but becomes much more prominent by further going into the polar region. The results suggest that the dominance of the inversion symmetry breaking may enhance the superconductivity rather than the actively discussed quantum fluctuation around the ferroelectric quantum critical point.
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| Free Research Field |
固体物理
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| Academic Significance and Societal Importance of the Research Achievements |
SrTiO3系の超伝導転移温度 Tc は、従来約 0.3 K であったが、元素置換によって強誘電を生成させると、Tc が大きく上昇し、0.75 K に達することを見出した。これまで、微量な酸素欠損の導入による電子ドーピング等、乱れの導入を最小限に抑える手法が重要視されてきたが、本研究では、対照的に、Sr/Ti それぞれのサイトに元素置換を施す方法を採用して、強誘電キュリー温度/キャリア濃度それぞれを制御し、強誘電/超伝導の相互関係を系統的に探索した。本研究により、本系の超伝導は、強誘電の導入によって増強されることが明らかとなり、本系の超伝導のメカニズム解明に大きな貢献をもたらすと考えられる。
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