Stacking ferroelectricity in two-dimensional van der Waals materials.

Miniaturization of ferroelectrics for technological applications has proven challenging due to the suppression of electric polarization caused by increasing depolarization fields as material thickness decreases. The emergence of ferroelectricity in two-dimensional (2D) van der Waals (vdW) materials offers a potential solution to this challenge, prompting significant research efforts over the past decade. While intrinsic 2D vdW ferroelectrics are scarce, polar stacking provides a more general approach to introducing ferroelectricity in these materials. This review revisits the fundamental concept of stacking ferroelectricity, complemented by symmetry analysis for constructing polar stackings, and both classical and quantum perspectives on the origin of stacking ferroelectrics. We present key advances in polarization dynamics and briefly summarize various physical phenomena directly coupled to stacking ferroelectricity, including multiferroic, magnetoelectric, and valleytronic effects, along with their related applications. Finally, we discuss future challenges and potential developments in the field of 2D stacking ferroelectricity.