日時：2022年5月17日（火）11時－12時
開催方法：オンライン

講師：林田 翔平 氏（スイス連邦工科大学チューリッヒ校）

題目：
Breakthrough in the study of frustrated ferro-antiferromagnets A2Cu2Mo3O12 (A = Rb, Cs)

要旨：
Linear-chain molybdate A2Cu2Mo3O12 (A = Rb, Cs) is one of the most intriguing linear frustrated ferro-antiferromagnets [1]. For over a decade extensive experimental and theoretical work focused on the unique magnetoelectric effect in Rb2Cu2Mo3O12 [2], and on spin-nematic Tomonaga-Luttinger liquid behavior in Cs2Cu2Mo3O12 [3]. Unfortunately, a lack of single-crystal samples has hampered any further progress.
In this talk, I will present our recent thermodynamic study using single-crystal samples, which have been grown in our group. The single-crystal study of both materials revealed that their magnetic and dielectric properties are even more complex and intriguing than originally thought [4,5,6]. Our comprehensive thermodynamic measurements mapped out the highly anisotropic low-temperature magnetic phase diagram for both materials [4,6]. Dielectric experiments revealed the Rb system to be a quantum multiferroic and enabled the first direct excitation-response measurements of critical susceptibility at a magnetic BEC quantum critical point [5]. For the Cs system, a host of exotic field-induced phases was discovered, including a presaturation phase that is likely to be a spin-nematic phase [6].

References
[1] M. Hase et al., Phys. Rev. B 70, 10426 (2004); J. Appl. Phys. 97, 10B303 (2005).
[2] H. Ueda et al., Phys. Rev. B 101, 140408(R) (2020).
[3] Y. Hoshino et al., JPS Conf. Proc. 3, 014012 (2014).
[4] S. Hayashida et al., Phys. Rev. B 100, 134427 (2019).
[5] S. Hayashida et al., Phys. Rev. Research 3, 033053 (2021).
[6] D. Flavián, S. Hayashida et al., Phys. Rev. B 101, 22408 (2020).

講演は日本語で行われます。

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関係所員：益田 隆嗣（ext.63415）
e-mail:　masuda@issp.u-tokyo.ac.jp