Ultrafast Polarization Switching via Laser-activated Ionic Migration in\n Ferroelectric CuInP$_2$S$_6$

As a layered ferroelectric material, CuInP2S6 has garnered significant\nattention for its robust ferroelectric state and potential applications in\nmemory devices. In this work, we demonstrate that with short laser pulses\nultrafast reversible polarization switching within hundreds of femtoseconds can\nbe achieved in ferroelectric CuInP$_2$S$_6$. Specifically, photoexcitation\ntriggers collective ionic migration and ferroelectricity reversal in\nCuInP$_2$S$_6$, revealing a novel pathway to access different ferroelectric\nphases through optical excitation. Our findings indicate that laser pulses\nsubstantially alter the transition barriers, promoting ionic transport\nfacilitated by the photodoping effect. This laser-induced ionic migration\nproves critical for enabling polarization transitions, offering a novel pathway\nto explore and control exotic quantum phases. These insights open exciting\npossibilities for manipulating ferroelectric states and electronic properties\non an unprecedented ultrafast timescale.\n