Antiferromagnets exhibit high-speed spin responses in the terahertz frequency
range and robustness against external magnetic fields, making them promising for nextgeneration
high-speed, high-density spintronic devices. Recently, two-dimensional van der
Waals magnetic systems, which possess rich antiferromagnetic ground states, have gained significant
attention and serve as ideal platforms for studying low-dimensional antiferromagnetic
physics. Detecting and controlling ultrafast spin dynamics in two-dimensional antiferromagnetic
systems will lay the foundation for high-speed spintronic device applications. Antiferromagnets
have no net macroscopic magnetization, making traditional optical methods, such as
magneto-optical effects, challenging for detecting antiferromagnetic order in equilibrium states.
However, in non-equilibrium states, the instantaneous magnetization generated by antiferromagnetic
spin dynamics allows the use of time-resolved magneto-optical Kerr effect to detect
coherent spin precession in antiferromagnets. Additionally, techniques such as linear dichroism
spectroscopy, terahertz emission spectroscopy, and second harmonic generation have been employed
in studying the dynamics of two-dimensional antiferromagnets. This paper introduces
recent experimental progress on ultrafast spin dynamics in two-dimensional van der Waals
antiferromagnetic systems, and briefly describes the coherent magnon excitations and corresponding
mechanisms in two-dimensional antiferromagnets, including inverse magneto-optical
effects/stimulated Raman scattering, orbital excitations, and exciton coupling. Furthermore,
this paper discusses the critical slowing down of spin dynamics due to spin-lattice coupling
effects and the amplification of coherent acoustic phonons.
