Identifying the transition pathway for ultrafast switching between distinct antiferromagnetic orders, while holding promise to realize unprecedentedly small and fast spin devices, remains largely unexplored. Herein, we show that rectifying structure with light can serve as a powerful tool to achieve nonthermal antiferromagnetic order switching in a monolayer antiferromagnet ${\mathrm{MnPSe}}_3$. By resolving the spin-phonon coupling strength, we identify a highly selective coupling of the magnetic order with a Raman-active ${\mathrm{E}}_g$ phonon. After resonantly pumping two degenerate infrared-active ${\mathrm{E}}_u$ modes, we obtain a new metastable out-of-equilibrium state holding shifted structure along the ${\mathrm{E}}_g$ mode. Such lattice distortion offers a sustained nonthermal driving field to trigger a phase switch from a Néel-type to a zigzag-type antiferromagnetic order within the coherent phonon lifetime. By varying the pumping polarization and intensity, we provide a parameter regime for realistic light-driven magnetic phase transitions. Such an ultrafast antiferromagnetism switch can be identified by pump-probe measurements of the order-parameter-like behavior in the second harmonic generation signal or absorption spectrum.

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• Light-induced magnetic effects
• Magnetic phase transitions
• Order parameters
• Spin-phonon coupling
• Ultrafast phenomena
• Antiferromagnets
• Density functional theory