Coherent phonon generation via exchange-mediated impulsive stimulated Raman scattering

In magnetic insulators, sub-gap laser pulses can alter spin exchange interactions via virtual excitations, providing a pathway to dynamically engineer magnetic Hamiltonians in solids. Here, we show that this gives rise to a phenomenon dubbed exchange-mediated impulsive stimulated Raman scattering (exchange-ISRS), where impulsive changes in exchange energy generate coherent phonons through magneto-elastic coupling. We develop a theoretical framework for understanding exchange-ISRS using a Floquet formalism, and then experimentally demonstrate its existence in the antiferromagnetic insulator MnPS₃ using broadband coherent phonon spectroscopy measurements. Our data suggest a transient enhancement of antiferromagnetic exchange energy in MnPS₃ and reveal its back-action on the lattice, which are crucial for developing realistic Floquet magnetic engineering protocols.