Magnetoelectric effect and nonreciprocal response of the quantum magnets

2020 Fiscal Year Final Research Report

• Project/Area Number: 17H02917
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Condensed matter physics II
• Research Institution: Tohoku University
• Principal Investigator: Kimura Shojiro 東北大学, 金属材料研究所, 准教授 (20379316)
• Co-Investigator(Kenkyū-buntansha): 川股 隆行 東北大学, 工学研究科, 助教 (00431601) ; 田中 秀数 東京工業大学, 理学院, 教授 (80188325)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: 量子スピン系 / マルチフェロイクス / 電気磁気効果 / 非相反応答

Outline of Final Research Achievements

The high-pressure electric polarization measurements of the spin dimer systems TlCuCl3 have revealed that the quantum fluctuation inherent in the spin dimer enhances the electric polarization, induced by the antiferromagnetic order owing to the magnon Bose-Einstein condensation, and gives soft nature to the ferroelectricity. By utilizing the soft nature, we have succeeded in fast switching of the nonreciprocal directional response to the microwave by the reversal of the electric polarization. We also have found that the optical transition from the spin singlet to the triplet state in KCuCl3 is induced by the oscillating electric fields of the terahertz electromagnetic wave.

Free Research Field

磁性物理学

Academic Significance and Societal Importance of the Research Achievements

螺旋磁気秩序誘起の強誘電発現の発見以来、大規模に研究が行われてきた電気磁気効果について、強い量子揺らぎを持つスピンダイマー系に特徴的な振る舞いを明らかにした。電気磁気効果と電子スピンの量子揺らぎの物理を結びつける新しい切り口のもと、量子揺らぎによる強誘電の増強と分極反転電場の低減、スピンシングレット-トリプレット状態間の振動電場による励起、方向二色性の電界スイッチングなどを観測しスピンの量子効果が交差相関を用いた物性制御に有効に働くことを示した。