Domain wall dynamics in trilayer sliding ferroelectric γ-InSe

Sliding ferroelectricity in van der Waals layers presents a novel mechanism for polarization switching. It features an ultralow energy barrier and high endurance, both governed by domain wall (DW) motion. Compared to bilayer sliding ferroelectric systems, trilayer and multilayer architectures introduce multiple sliding interfaces, causing polarization switching to involve intermediate domain states and coupled DW dynamics rather than a simple single-interface process. Nonetheless, the realization of these multistate switching functionalities is strongly dependent on DWs dynamics, which become substantially more intricate in these layered architectures and are still poorly understood. Here, using trilayer γ -InSe as a minimal prototype of multilayer sliding ferroelectrics, we systematically investigate the static and dynamic properties of DWs by combining density functional theory calculations and machine-learning-assisted molecular dynamics simulations. The simulation results reveal that adjacent layers form DWs at distinct locations, separated by nonpolar domains situated between the upward- and downward-polarized ferroelectric domains, which markedly differs from the bilayer structure. Under external electric fields, polarization switching proceeded through distinct kinetic stages, with DW motion exhibiting a parabolic displacement-time relationship that transitioned from acceleration to DW velocity at higher fields. Notably, the collective motion of the DWs indicates the presence of significant inter-DW interactions. This work provides an atomistic picture of intermediate nonpolar domains and staged DW-mediated switching dynamics in trilayer sliding ferroelectric γ -InSe, providing microscopic insight into DW-mediated switching in multilayer sliding ferroelectrics.