Giant chiral magnetoelectric oscillations in a van der Waals multiferroic

• 成果类型: Article
• 署名作者: Gao, Frank Y.; Peng, Xinyue; Cheng, Xinle; Boestrom, Emil Vinas; Kim, Dong Seob; Jain, Ravish K.; Vishnu, Deepak; Raju, Kalaivanan; Sankar, Raman; Lee, Shang-Fan; Sentef, Michael A.; Kurumaji, Takashi; Li, Xiaoqin; Tang, Peizhe; Rubio, Angel; Baldini, Edoardo
• 署名单位: University of Texas System; University of Texas Austin; University of Texas System; University of Texas Austin; Max Planck Society; University of Basque Country; Academia Sinica - Taiwan; National Tsing Hua University; University of Bremen; University of Bremen; California Institute of Technology; Simons Foundation; Flatiron Institute
• 刊物名称: Nature
• ISSN/ISSBN: 0028-6137
• DOI: 10.1038/s41586-024-07678-5
• 发表日期: 2024-08-08
• 页码: 273-+
• 关键词: magnetic-properties; spin; ORDER; nii2

摘要

Helical spin structures are expressions of magnetically induced chirality, entangling the dipolar and magnetic orders in materials(1-4). The recent discovery of helical van der Waals multiferroics down to the ultrathin limit raises prospects of large chiral magnetoelectric correlations in two dimensions(5,6). However, the exact nature and magnitude of these couplings have remained unknown so far. Here we perform a precision measurement of the dynamical magnetoelectric coupling for an enantiopure domain in an exfoliated van der Waals multiferroic. We evaluate this interaction in resonance with a collective electromagnon mode, capturing the impact of its oscillations on the dipolar and magnetic orders of the material with a suite of ultrafast optical probes. Our data show a giant natural optical activity at terahertz frequencies, characterized by quadrature modulations between the electric polarization and magnetization components. First-principles calculations further show that these chiral couplings originate from the synergy between the non-collinear spin texture and relativistic spin-orbit interactions, resulting in substantial enhancements over lattice-mediated effects. Our findings highlight the potential for intertwined orders to enable unique functionalities in the two-dimensional limit and pave the way for the development of van der Waals magnetoelectric devices operating at terahertz speeds.