Towards sliding ferroelectricity in two-dimensional van der Waals materials

Sliding ferroelectricity originates from lateral interlayer shifts in stacked two-dimensional van der Waals materials, where the relative sliding of one layer over another breaks inversion symmetry and generates a switchable polarization. As a novel form of ferroelectricity, it enables intrinsically nonpolar crystals to exhibit ferroelectric behavior simply by adopting specific stacking arrangements, thereby greatly expanding the pool of potential ferroelectric candidates. This distinctive mechanism also endows sliding ferroelectrics with entirely new functionalities. For example, their ultralow switching barriers allow exceptional endurance over millions to trillions of switching cycles and enable ultrafast polarization reversal on sub-nanosecond timescales, far surpassing the properties of conventional ferroelectric materials. In this review, we begin by discussing the theoretical models of sliding ferroelectricity, followed by an overview of the corresponding experimental verification and characterization techniques. Building on this understanding, we provide an in-depth discussion of recent advances, including polarization-switching kinetics, domain wall dynamics, topological polar structures, multiple polarization states, optical probing of polarization, and active modulation strategies. Finally, we address the remaining challenges and highlight the broad prospects for future research and applications of two-dimensional sliding ferroelectric materials.