Ferroelastic domain switching by ultrafast photoinduced strain
The crystal lattice underpins the fundamental properties of condensed matter, with ferroic order emerging sensitively from atomic coordination. Manipulating the lattic therefore promises a direct way to switch ferroics between their states. Infrared excitation provides an efficient pathway to drive lattice motion and generate transient crystal deformations and strains. Ferroelastics constitute a uniquely direct platform for such control, their order parameter being strain itself. However, whether ultrafast laser-induced lattice distortions can switch ferroelastic order remains unknown. Here we use ultrafast pump-probe microscopy to demonstrate that a single high-amplitude infrared pulse induces strain within the first nanosecond, followed by ferroelastic domain switching several nanoseconds later. The spatial distribution follows that expected from the photoinduced strain field, while their temporal evolution is closely coupled to the strain dynamics. Our observations identify transient strain as the driving field for ferroelastic switching and suggest a general lattice-mediated pathway for controlling ferroic order using infrared light.