Quantum Electrodynamics in Solids: Dynamical Properties of Dirac and Weyl Materials

2022 Fiscal Year Final Research Report

• Project/Area Number: 18K03482
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 13020:Semiconductors, optical properties of condensed matter and atomic physics-related
• Research Institution: The University of Tokyo
• Principal Investigator: MAEBASHI Hideaki 東京大学, 大学院理学系研究科(理学部), 特任研究員 (30361661)
• Co-Investigator(Kenkyū-buntansha): 松浦 弘泰 東京大学, 大学院理学系研究科(理学部), 助教 (40596607)
• Project Period (FY): 2018-04-01 – 2023-03-31
• Keywords: ディラック電子系 / ワイルフェルミオン系 / 量子電磁力学 / 軌道磁性 / 核磁気緩和 / ノーダルライン半金属

Outline of Final Research Achievements

Theoretical studies on the dynamical responses of Dirac-Weyl fermion systems have been carried out using field-theoretical methods (QED in solids) corresponding to quantum electrodynamics, and the following results were obtained: (1) The relationship between the electric and magnetic responses in Dirac electron systems was clarified. (2) We developed a theory of nuclear magnetic relaxation due to orbital currents in Weyl fermion systems and clarified the effect of disorder on it. (3) The large orbital diamagnetisms of molecular solids α-(BETS)2I3 and HMTSF-TCNQ were quantitatively evaluated and found to be in good agreement with experimental results. (4) The transport and thermoelectric properties of various Dirac-type materials were theoretically predicted.

Free Research Field

物性理論

Academic Significance and Societal Importance of the Research Achievements

本研究は、ディラック電子系物質と量子電磁力学(QED)では特徴的な長さやエネルギーの尺度が大きく異なるにもかかわらず、それらの電気的性質と磁気的性質の間には共通の関係があるという階層構造を明確にしたという点で学術的意義がある。さらに、本研究で見出したディラック電子系物質における軌道反磁性と電気伝導の間に成立する関係等の基礎学理、またディラック電子系関連物質の発見や解析は、磁性と輸送が絡んだ社会的ニーズがある新奇機能性物質を開拓する際の指針につながると期待される。