Artificial control of superconducting transition temperature and its applications to detector devices

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K21011
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 21:Electrical and electronic engineering and related fields
• Research Institution: Institute of Physical and Chemical Research
• Principal Investigator: Otani Chiko 国立研究開発法人理化学研究所, 光量子工学研究センター, チームリーダー (50281663)
• Project Period (FY): 2020-07-30 – 2022-03-31
• Keywords: 超伝導 / メタマテリアル / マイクロ波 / MKIDs

Outline of Final Research Achievements

he superconducting transition temperatures (Tc) have been considered to be material-specific values, but recently it has been pointed out that, in superconducting hyperbolic metamaterial structures, the effective dielectric constant is asymmetric in the parallel and vertical directions of the film, possibly enhancing the Cooper pair’s attracting interaction. In this study, we fabricated 3- and 5-layer MKIDs using a well-established and reproducible superconductor(Al)-insulator(AlOx) multilayer thin films (Al layer thickness of about 8 nm) to verify the superconducting transition temperatures by measuring microwave transmission gain between 2-8 GHz. Then, Tc values of 1.7-1.8 K were observed for Al thin films (bulk Tc~1.15 K), but the effect of the hyperbolic metamaterial was not confirmed.

Free Research Field

テラヘルツ工学、超伝導検出器

Academic Significance and Societal Importance of the Research Achievements

仮に、超伝導ハイパボリックメタマテリアル構造を導入した影響でTcが変化するならば、超伝導薄膜の膜構造で人工的に制御できることとなり、より高温での超伝導状態の実現や民生利用に繋がる衝撃的な事実となる可能性があったが、今回の検証では、そのような事実は確認できず、ハイパボリックメタマテリアル構造がCooper Pairの引力相互作用に影響を与えると結論づけるには至らなかった。