Is There A Pure Electronic Ferroelectric?

Different from traditional ferroelectrics whose polarization stems from ionic displacements mediated by phonons, electronic ferroelectrics exhibit spontaneous polarization originating from polar electronic ordering. Such electronic mechanisms promise devices with ultrafast switching speeds, lower energy consumption, and enhanced resilience to fatigue and depolarization fields inherent in conventional ferroelectrics. While early candidates are restricted to rare oxides and organic charge-transfer salts, emerging systems—particularly 2D van der Waals moiré heterostructures—have significantly broadened this materials landscape. This review comprehensively examines ferroelectrics governed by electronic mechanisms, categorizing them according to microscopic origins, including spin correlations, charge ordering, orbital interactions, charge-transfer instabilities, and excitonic phenomena. Representative materials span multiferroics, molecular crystals, and engineered van der Waals architectures. Crucially, we evaluate whether their ferroelectricity qualifies as purely electronic—defined by the absence of ionic displacements during polarization reversal—synthesizing recent theoretical and experimental advances to establish a unified framework for this evolving paradigm.