Relation between the charge fluctuation and superconductivity in organic superconductors studied by STM/STS

2022 Fiscal Year Final Research Report

• Project/Area Number: 17K05526
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Condensed matter physics II
• Research Institution: Hokkaido University
• Principal Investigator: Ichimura Koichi 北海道大学, 工学研究院, 准教授 (50261277)
• Co-Investigator(Kenkyū-buntansha): 松浦 徹 福井工業高等専門学校, 電気電子工学科, 准教授 (60534758)
• Project Period (FY): 2017-04-01 – 2023-03-31
• Keywords: 超伝導 / 電荷秩序 / 走査トンネル顕微鏡 / 有機導体 / 強相関電子系

Outline of Final Research Achievements

An organic superconductor, which exhibits the charge ordering, was studied by low temperature scanning tunneling microscope (STM) to elucidate the role of the charge degrees of freedom in highly correlated electron systems. The charge disproportionation was observed by scanning tunneling spectroscopy (STS) in the charge ordering phase. We found that the charge disproportionation corresponds to the spatial modulation of the charge ordering gap. The charge disproportionation exists in the superconducting state, indicating that the superconductivity and the charge ordering coexist. It suggests that the charge fluctuation due to the long range (offsite) Coulomb interaction correlates to the superconductivity.

Free Research Field

電子物性物理学

Academic Significance and Societal Importance of the Research Achievements

本研究により電荷秩序相での電子分布がナノメートルスケールで実空間観測できた。ここで確立したトンネルスペクトルから電子密度分布を得る方法は、強相関電子系を研究するうえで有用な手段である。
また、電荷ゆらぎが深く関与する新しい超伝導発現機構が示唆された。