Nonthermal dynamics of ferroelectric polarization in a van der Waals multiferroic

Type-II multiferroics are unique in hosting ferroelectricity driven by magnetic orders, offering stronger magnetoelectric coupling than any other known materials. While the formation of ferroelectric polarization and magnetization is well understood, their light-driven dynamics remain elusive. Here, using time-resolved rotational anisotropy second harmonic generation (tr-SHG), we reveal nonthermal dynamics of ferroelectric polarization under above-gap light excitation in the van der Waals multiferroic NiI₂. The ferroelectric polarization shows an immediate drop within the time resolution (~150 fs), followed by electromagnon oscillations and a slow recovery. Notably, the recovery time shortens with increasing fluence, resembling bimolecular recombination. Our findings demonstrate that polarization dynamics are driven by photo-excited carriers that screen the ferroelectric polarization. Additionally, we discuss the interplay between ferroelectricity and magnetization, highlighting new possibilities for controlling intertwined orders in complex materials.