Study of spin-driven chirality

2018 Fiscal Year Final Research Report

• Project/Area Number: 17H04845
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Condensed matter physics I
• Research Institution: The University of Tokyo
• Principal Investigator: Takahashi Youtarou 東京大学, 大学院工学系研究科(工学部), 准教授 (30631676)
• Project Period (FY): 2017-04-01 – 2019-03-31
• Keywords: 光物性 / マルチフェロイクス / テラヘルツ分光

Outline of Final Research Achievements

Chirality has been a fundamental concept in many fields including physics, optics, chemistry and biology. Usually the chiraty is caused by asymmetry of the chemical structure of matter. On the other hand, the chirality induced by the long range orders of spin has been attracting increasing attention.
In this work, we study the fundamental characteristics and novel functionality of magnetically-induced chirality on helimagnets by using the terahertz polarimetry. On the symmetric chemical lattice, the enhanced natural optical activity was observed on the resonance of electromagnon. The temporal control of the natural optical activity was demonstrated by applying the electric field pulses. The chiral domain wall dynamics was measured by the using the natural optical activity and the dynamical phase transitions of the domain wall was clearly observed. These results enable us to the comprehensive study of dynamical phase transitions.

Free Research Field

光物性

Academic Significance and Societal Importance of the Research Achievements

カイラリティは対称性の破れを示す普遍的な概念である。一般的にはカイラリティは結晶や分子中の原子位置によって生じるが、スピン構造によっても結晶構造とは独立にカイラリティを持ちうる。スピン構造由来のカイラリティの最も基本的な特性である、自然旋光性をテラヘルツ帯のエレクトロマグノンの共鳴で観測することに成功し、カイラリティが外場で制御しうることを明らかにした。この結果はスピン由来のカイラリティの持つ基礎特性を解明しただけではなく、スピン構造特有の機能性を持ちうることを示したものである。