Sliding Ferroelectricity in 2D Materials: Related Physics and Extensions

The prediction of so-called "sliding ferroelectricity" has been confirmed recently in a series of experiments that have stimulated remarkable interest. Such ferroelectricity exists widely and exists only in 2D van der Waals stacked layers, where the vertical electric polarization is switched by in-plane interlayer sliding. The unique combination of intralayer stiffness and interlayer slipperiness of 2D van der Waals layers greatly facilitate such switching while still maintaining environmental and mechanical robustness at ambient conditions. This discovery broadens 2D ferroelectrics from very few material candidates to most of known 2D materials. Their low switching barriers enable high-speed data writing with low energy cost. In addition to its unique switching mode, other related new physics like Moiré ferroelectricity, metallic ferroelectricity, ferroelectric nonlinear anomalous Hall effect, sliding multiferroic couplings, as well as related extensions like semi-sliding ferroelectricity, are emerging.