Unidirectional Electric Field Enables Reversible Ferroelectric Domain Engineering

The deterministic control of ferroelectric polarization via an external field is critical for advancing the technologies of modern information storage. Conventionally, reversible and cyclic polarization switching in ferroelectric materials requires alternating electric fields with opposite (±) orientations. The present work demonstrates that this scenario can be circumvented in the van der Waal (vdW) ferroelectrics CuInP₂S₆. Conceptionally, by a fixed unidirectional electric field, effective ferroelectric domain engineering with reversible and cyclic switching is accomplished, relying on highly controllable Cu ion migration across vdW gaps. It further unveils the remarkable “shape memory” effect of manipulated domains, and the unprecedented ability to electrically “write” domain configurations. Our findings not only deepen the understanding of ion-coupled ferroelectric behavior, but also provide insights into origin of negative capacitance and the quantized charge transport, paving the way for emerging storage technologies and low-power neuromorphic applications.