Bartram F Michael, Li Meng, Liu Liangyang, Xu Zhiming, Wang Yongchao, Che Mengqian, Li Hao, Wu Yang, Xu Yong, Zhang Jinsong, Yang Shuo, Yang Luyi
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.
State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China.
Sci Bull (Beijing). 2023 Nov 30;68(22):2734-2742. doi: 10.1016/j.scib.2023.10.003. Epub 2023 Oct 10.
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 MnBiTe 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.
原子级薄的范德华磁性材料不仅为在二维（2D）极限下探索基础物理提供了一个丰富的平台，还为新型超快功能器件创造了大量机会。在此，我们系统地研究了少层拓扑反铁磁MnBiTe晶体中的超快磁化动力学和自旋波动力学，作为层数、温度和磁场的函数。我们发现激光诱导的（去）磁化过程可用于精确追踪不同磁场区域中的不同磁态，包括呈现出明显的奇偶层数效应。此外，在时域中光学产生并直接观测到了具有数十吉赫兹频率的强磁场依赖的反铁磁磁振子模式。值得注意的是，我们发现不仅可以在时间分辨磁光克尔效应中观测到磁化和磁振子动力学，还能在时间分辨反射率中观测到，这表明磁态与电子结构之间存在强相关性。这些测量首次全面概述了这种新型二维反铁磁体中的超快自旋动力学，为二维反铁磁自旋电子学和磁子学的潜在应用以及对磁化和拓扑量子态的超快控制的进一步研究铺平了道路。
