Topological piezoelectricity in bulk ferroelectrics

Ferroelectric topological vortex domains have attracted interest for their topologically protected properties and potential in next-generation electronics. Although extensive research has focused on low-dimensional nanostructures, the role of vortex domains in bulk ferroelectrics remains poorly understood. Here we identify topological vortex structures in bulk Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ crystals and demonstrate their direct role in enhancing the piezoelectric response, establishing a mechanistic link between vortex structures and macroscopic performance. We develop a straightforward and scalable method, mechanically assisted electrical poling, to engineer vortex domain density, which increases the vortex core density from 0.01 μm^-2 in conventionally poled samples to 21 μm^-2. This controlled domain engineering leads to a remarkable improvement in the piezoelectric response, primarily attributed to localized strain surrounding the vortex cores. This study advances our understanding of topological structures in bulk ferroelectrics, and opens up a practical pathway to engineer high-performance ferroelectrics for device applications.