Multi-parameter control of strongly correlated materials using field-effect device structures

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K03730
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: Toho University
• Principal Investigator: Kawasugi Yoshitaka 東邦大学, 理学部, 講師 (40590964)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 超伝導トランジスタ / モット絶縁体 / 分子性導体

Outline of Final Research Achievements

In strongly correlated materials, where the Coulomb interaction between electrons dominates the physical properties, it is known that a small amount of parameter control by doping or pressure can induce a dramatic change in electronic state, as typified by the superconducting transition, and device applications are anticipated. In this study, we fabricated field-effect transistor devices using strongly correlated organic materials and succeeded in observing a steep insulator/superconductor transition by precisely controlling parameters such as doping by gate voltage and pressure by substrate strain. On the doping-strain phase diagram, the superconducting phase was found to surround the insulating phase, which is asymmetric with respect to the electron-hole doping, reflecting the electron-hole asymmetry of the anisotropic triangular lattice.

Free Research Field

物性実験

Academic Significance and Societal Importance of the Research Achievements

電子間のクーロン相互作用が物性を支配する強相関物質では、ドーピングや圧力によるわずかなパラメータ制御で超伝導転移に代表される劇的な電子状態の変化が起こることが知られており、デバイス応用が期待されている。しかし一般的なパラメータ制御は化学的な元素置換や高圧力を用いて行われるため、同一の試料で電子状態を変化させることは容易ではない。本研究では有機強相関物質を用いることで1ボルト程度の電圧、1%程度のひずみで同一試料における超伝導転移を実現してデバイス利用の可能性を示すとともに、三角格子を持つ強相関電子系において超伝導が現れる条件(超伝導相図)を示すことに成功した。