Polar topology in self-assembled PbTiO₃ ferroelectric nano-islands

The topological domains in ferroelectrics have garnered significant attention for their potential applications in nanoelectronics. However, current research is predominantly limited to rhombohedral BiFeO₃ materials. To validate the universality of topological domains in non-rhombohedral ferroelectrics, it is crucial to explore the existence and characteristics of topological states in alternative material systems. In this work we successfully construct topological polar structures in PbTiO₃ nano-islands with a tetragonal structure. Furthermore, the topological structures can be well manipulated by electric field and mechanical stress, making them switchable between center-divergent structure and center-converging types. Phase-field simulations revealed that the aggregation and redistribution of free charges play a decisive role in the formation and manipulation of topological states. These findings not only verify the feasibility of constructing topological domains in universal ferroelectrics, but also validate the multiple manipulability of these topological domains, displaying their significant potential in high-density nonvolatile memory devices.