Development of an innovative evaluation method for superconducting devices due to phase transition on two-dimensional superconductors

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K06390
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Electron device/Electronic equipment
• Research Institution: Kumamoto University
• Principal Investigator: ICHIKAWA Fusao 熊本大学, 大学院先端科学研究部(理), 教授 (30223085)
• Co-Investigator(Kenkyū-buntansha): 牧瀬 圭正 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, 主任研究員 (60363321) ; 篠崎 文重 九州大学, 理学研究院, 名誉教授 (80117126)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 超伝導デバイス / 超伝導ゆらぎ / 超伝導－絶縁体転移 / デバイス評価

Outline of Final Research Achievements

In order to investigate the effects of superconducting fluctuations and superconducting-insulator transition (SIT) phenomena that occur with the reduction of dimension of samples on superconducting devices, these phenomena were investigated for Mo-based superconducting thin films: MoN, MoRu, MoRe, and MoRe-N. For the relationship between superconducting transition temperature and sheet resistance in the normal state of these films with different thickness, the result is consistent with the electron localization model. The relation between sheet resistance and disorder depends on the material. On the other hand, the field-tuned SI transition was observed for MoN thin films, and all the data collapse onto two separate curves as a function of the scaling variable. Peaks were observed in the magnetic field dependence of the Hall resistance. The mechanism may be different between thickness-tuned SIT and magnetic field-tuned SIT.

Free Research Field

低温物性物理学

Academic Significance and Societal Importance of the Research Achievements

極限的な微細加工技術によって実現される超伝導デバイスでは、次元低下に伴って応答速度の低下や雑音増加が起こる。そこで２次元超伝導相転移から得られる諸特性を定量的にデバイスパラメータ化し、デバイスの限界性能を見極める評価方法を開発することが求められる。本研究ではMo系超伝導体であるMoN、MoRu、MoRe、MoRe-N薄膜に対して実験を行った。その結果、元素の種類を変えても諸特性は近い値を示すが、乱れの種類や導入に左右されることがわかった。