Photoinduced Ultrafast Phase Transition in Bilayer CrI3

In two-dimensional magnets, the ultrafast photoexcitedmethod representsa low-power and high-speed method of switching magnetic states. BilayerCrI(3) (BLC) is an ideal platform for studying ultrafastphotoinduced magnetic phase transitions due to its stacking-dependentmagnetic properties. Here, by using time-dependent density functionaltheory, we explore the photoexcitation phase transition in BLC fromthe R- to M-stacked phase. This process is found to be induced byelectron-phonon interactions. The activated A (g) and B (g) phonon modes in the xy direction drive the horizontal relative displacementsbetween the layers. The activated A (g) modein the z direction leads to a transition potentialreduction. Furthermore, this phase transition can invert the signof the interlayer spin interaction, indicating a photoinduced transitionfrom ferromagnet to antiferromagnet. This investigation has profoundimplications for magnetic phase engineering strategies.