Recently, Floquet engineering has attracted much attention as a powerful approach to control the microscopic interactions in quantum materials using light. In this framework, periodic light fields dynamically tune the parameters of a material's Hamiltonian. In magnetic insulators, sub-gap laser pulses can modify spin-exchange interactions via virtual excitations, avoiding heating or real carrier generation.
In this talk, I will introduce a new mechanism called exchange-mediated impulsive stimulated Raman scattering (echange-ISRS), where ultrafast light pulses induce a transient change in the magnetic exchange energy, which in turn drives coherent phonon oscillations. We experimentally demonstrate this effect in the antiferromagnetic insulator MnPS₃ using time-resolved broadband reflection spectroscopy, which shows a non-trivial temperature dependence. Supported by a Floquet-based theoretical framework, our results suggest that sub-gap optical driving transiently enhances antiferromagnetic exchange interactions, leading to an additional spin-originated driving force on the lattice. This study highlights a new way to probe light-induced changes in the spin Hamiltonian, with implications for practical ways to control magnetic properties in quantum materials on ultrafast timescales [1].
[1] R. Noguchi et al., under review.