Real-time observation of magnetization and magnon dynamics in a two-dimensional topological antiferromagnet MnBi2Te4

F Michael Bartram; Meng Li; Liangyang Liu; Zhiming Xu; Yongchao Wang; Mengqian Che; Hao Li; Yang Wu; Yong Xu; Jinsong Zhang; Shuo Yang; Luyi Yang

doi:10.1016/j.scib.2023.10.003

Real-time observation of magnetization and magnon dynamics in a two-dimensional topological antiferromagnet MnBi₂Te₄

Sci Bull (Beijing). 2023 Nov 30;68(22):2734-2742. doi: 10.1016/j.scib.2023.10.003. Epub 2023 Oct 10.

Authors

F Michael Bartram¹, Meng Li², Liangyang Liu², Zhiming Xu², Yongchao Wang³, Mengqian Che², Hao Li⁴, Yang Wu⁵, Yong Xu⁶, Jinsong Zhang⁷, Shuo Yang⁸, Luyi Yang⁹

Affiliations

¹ State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China; Department of Physics, University of Toronto, Toronto M5S 1A7, Canada.
² State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China.
³ Beijing Innovation Center for Future Chips, Tsinghua University, Beijing 100084, China.
⁴ Tsinghua-Foxconn Nanotechnology Research Center, Department of Physics, Tsinghua University, Beijing 100084, China.
⁵ Tsinghua-Foxconn Nanotechnology Research Center, Department of Physics, Tsinghua University, Beijing 100084, China; College of Math and Physics, Beijing University of Chemical Technology, Beijing 100029, China.
⁶ State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China; Frontier Science Center for Quantum Information, Beijing 100084, China; Collaborative Innovation Center of Quantum Matter, Beijing 100084, China; RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan.
⁷ State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China; Frontier Science Center for Quantum Information, Beijing 100084, China; Hefei National Laboratory, Hefei 230088, China.
⁸ State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China; Frontier Science Center for Quantum Information, Beijing 100084, China; Collaborative Innovation Center of Quantum Matter, Beijing 100084, China; Hefei National Laboratory, Hefei 230088, China.
⁹ State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China; Department of Physics, University of Toronto, Toronto M5S 1A7, Canada; Frontier Science Center for Quantum Information, Beijing 100084, China; Collaborative Innovation Center of Quantum Matter, Beijing 100084, China. Electronic address: luyi-yang@mail.tsinghua.edu.cn.

PMID: 37863774
DOI: 10.1016/j.scib.2023.10.003

Abstract

Atomically thin van der Waals magnetic materials have not only provided a fertile playground to explore basic physics in the two-dimensional (2D) limit but also created vast opportunities for novel ultrafast functional devices. Here we systematically investigate ultrafast magnetization dynamics and spin wave dynamics in few-layer topological antiferromagnetic MnBi₂Te₄ crystals as a function of layer number, temperature, and magnetic field. We find laser-induced (de)magnetization processes can be used to accurately track the distinct magnetic states in different magnetic field regimes, including showing clear odd-even layer number effects. In addition, strongly field-dependent AFM magnon modes with tens of gigahertz frequencies are optically generated and directly observed in the time domain. Remarkably, we find that magnetization and magnon dynamics can be observed in not only the time-resolved magneto-optical Kerr effect but also the time resolved reflectivity, indicating strong correlation between the magnetic state and electronic structure. These measurements present the first comprehensive overview of ultrafast spin dynamics in this novel 2D antiferromagnet, paving the way for potential applications in 2D antiferromagnetic spintronics and magnonics as well as further studies of ultrafast control of both magnetization and topological quantum states.

Keywords: 2D topological antiferromagnet; Magnonics; Spintronics; Ultrafast magnetization dynamics; Ultrafast magnon dynamics; Ultrafast spectroscopy.