Theoretical study of Higgs mode in magnetic materials

2016 Fiscal Year Final Research Report

• Project/Area Number: 26400332
• 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: Shizuoka University
• Principal Investigator: Matsumoto Masashige 静岡大学, 理学部, 教授 (20281058)
• Co-Investigator(Renkei-kenkyūsha): HASE Masashi 物材機構, 中性子散乱グループリーダー (40281654) ; KUROE Haruhiko 上智大学, 理工学部, 准教授 (40296885) ; MASUDA Takatsugu 東京大学, 物性研究所, 准教授 (90313014)
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: ヒッグスモード / 振幅モード / 磁気励起 / 量子スピン / 量子相転移 / 電気磁気効果 / エレクトロマグノン / マルチフェロイクス

Outline of Final Research Achievements

We presented a generalized theory for magnetic excitations in interacting spin cluster systems and applied it to specific magnetic materials, such as spin dimer, trimer, and tetramers. Collaborating with experimental groups, we confirmed that a Higgs amplitude mode was actually observed by inelastic neutron scattering in a two-dimensional (2D) quantum spin system, while it has been believed to be difficult to observe it in 2D systems. The reason is that the Higgs amplitude mode is located at low-enegy region in the vicinity of a quantum critical point and that it is protected from decaying into a pair of Nambu-Goldstone modes (NG-modes) by opening of a small energy gap in the NG-mode which originates from a weak easy-axis anisotropy. We also presented a theory of magnetoelectric effects to detect Higgs amplitude. We applied the theory to specific spin systems and confirmed the reliability of the theory.

Free Research Field

物性理論