  The switching dynamics of ferroelectric materials is a crucial intrinsic
property which directly affects the operation and performance of ferroelectric
devices. In conventional ferroelectric materials, the typical ferroelectric
switching mechanism is governed by a universal process of domain wall motion.
However, recent experiments indicate that Van der Waals ferroelectric CuInP2S6
possesses anomalous polarization switching dynamics under an electric field. It
is important to understand the switching dynamics, but it remains theoretically
unexplored in CuInP2S6 due to the lack of description of its order-disorder
phase transition characteristics by density functional theory. Here, we employ
a machine-learning potential trained from the first principles density
functional theory dataset to conduct the large-scale atomistic simulations of
temperature-driven order-disorder ferroelectric phase transition in CuInP2S6.
Most importantly, it is found that the electric field-driven polarization
switching in CuInP2S6 is mediated by single Cu dipole flip, rather than
conventional domain wall motion mechanism. This intrinsic unconventional
switching behavior can be attributed to the competition between the energy
barrier of domain wall motion and single dipole flip.
