Switching on Antiferroelectrics

Antiferroelectrics attract broad attention due to their unusual physical characteristics, chief among which is the double-hysteresis loop that separates their antipolar ground state from the voltage-induced polar phase, which is promising for applications in energy storage and electrocaloric cooling. However, their defining features (antipolar ground state and double-hysteresis loops) are increasingly challenged: materials with non-collinear and/or hybrid polar-antipolar order have been discovered, and double-hysteresis has been realized in materials without a conventional antipolar ground state. These developments add to the intensifying interest in fundamental and practical aspects of antiferroelectrics, and call for a fresh look at antiferroelectricity. In this Perspective, we provide an updated and all-encompassing definition of antiferroelectricity, discuss material systems with new antipolar orders and/or engineered double hysteresis, and reflect on emergent properties and theoretical approaches. This work casts a bird's eye view on the rapidly evolving trends that are shaping up the research on ferroics with antipolar order.