Sliding ferroelectricity: theory, experiment, and potential applications

In recent years, two-dimensional (2D) ferroelectrics have stimulated remarkable interest. Notably, the recently proposed concept of sliding ferroelectricity suggests that for most 2D materials, vertical polarization can be induced through interlayer stacking in their bilayers and multilayers, which are switchable upon interlayer sliding driven by a vertical electric field. Such sliding ferroelectricity has been extensively verified experimentally in a series of van der Waals systems. This paper will provide a concise review of the latest theoretical and experimental developments in sliding ferroelectrics, as well as their potential applications. The unique sliding mechanism significantly reduces the switching barrier while ensuring thermal stability, and also enables high-speed, low energy cost, and fatigue-resistant data writing, all of which have been confirmed experimentally. The coupling of sliding ferroelectricity with intrinsic physical properties of 2D monolayers (magnetism, excitonics, superconductivity, valleytronics, nontrivial topology, phonon chirality, etc.), allows for non-volatile electrical control of those properties. The related physics, like Moiré ferroelectricity, metallic ferroelectricity, and the ferroelectric nonlinear anomalous Hall effect, have greatly enriched ferroelectric physics, providing a broad platform for exploring novel physical phenomena and developing new electronic devices. Currently, large-scale growth of sliding ferroelectric single crystals has been achieved experimentally. The superior performance of transistors, neuromorphic memristors, optoelectronics, and other devices based on sliding ferroelectrics has been verified. The unoptimized flipping speed and fatigue resistance are already comparable to the best performance of prevalent ferroelectric devices, indicating a promising future.