Elucidation of itinerant magnetism in narrow-gap semiconductor FeSi by investigating ultra-high-field properties

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K03710
• 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: Institute of Physical and Chemical Research (2021); The University of Tokyo (2019-2020)
• Principal Investigator: Nakamura Daisuke 国立研究開発法人理化学研究所, 創発物性科学研究センター, 研究員 (70613628)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: ナローギャップ半導体 / 超強磁場 / 鉄シリサイド / 電気伝導 / 高周波

Outline of Final Research Achievements

The evolution of energy band structure in strongly correlated semiconductor FeSi is investigated by the high magnetic field transport properties. Because the band gap energy of FeSi is less than 100 meV, the energy band structure could be drastically modified by the Zeeman energy. In this project, I used the electromagnetic flux compression megagauss generator in the Institute for Solid State Physics, University of Tokyo, and measured the high-frequency electrical conductivity up to the ultra-high field region of 500 T. As a result, I clarified that the field-induced semiconductor-metal transition takes place at 270 T, by closing the energy band gap. In addition, I observed the anomaly in the magnetoconductivity below 80 K, which might originate from the hopping motion of quasiparticle in the in-gap states.

Free Research Field

強磁場物性

Academic Significance and Societal Importance of the Research Achievements

強相関半導体FeSiにおいて超強磁場により誘起される電気伝導物性の変化を詳細に調査した。100テスラを大きく超える超強磁場領域でのこのような研究は発生磁場の信頼性および物性計測の再現性などの観点から、過去にほとんど例を見ないものである。そのため本研究は当該分野の物性計測技術の進展を顕著に示すものであり、今後多様な強相関半導体研究への展開が期待できる。例えば、伝導電子と遍歴電子との混成による近藤効果が生じ、極低温でトポロジカル絶縁体としての性質を示す近藤半導体SmB6に関して、現在研究が進行中である。