In this issue we present three papers on the topological properties or structure of ferroelectrics, which are interlinked.
Topology is the branch of mathematics concerned with the continuous deformation of geometries, one of the main conclusions of which is that geometries cannot be distorted arbitrarily into any shape; that is, certain structures are topologically invariant. This may seem like a far cry from materials science, but science has a way of connecting fields as seemingly widely separated as nuclear physics and magnetism. Consider the magnetic skyrmion, so-called because its particle-like and chiral spin structures are topologically protected and cannot be deformed into bulk ferromagnetic phases. This is analogous to solutions to a nonlinear field theory by Tony Skyrme of interacting pions that resulted in stable particles. These magnetic skyrmions were first observed in 2009, and have potential for high-density information storage. It was almost a decade later before skyrmions (pictured) and similar topological structures were observed in another ferroic; ferroelectrics that possess permanent polarization and history-dependent switching behaviour under electric field. Complex heterostructures or nanostructures are required to balance competing energetics to stabilize topological structures, potentially limiting experimental accessibility and applications of these systems.