Artificial creation and separation of a single vortex-antivortex pair in a ferroelectric flatland

Abstract

Topological defects have received much attention due to their stability against perturbations and potential applications in nonvolatile high-density memory. Topologically non-trivial textures can be compelled by constraints on boundary condition, geometrical structure, and curved space. Ferroelectric vortices have been realized in various finite-sized nanostructures that allow such constraints to be produced. However, manipulation of topological excitations in otherwise topologically trivial flat ferroelectrics remains a tantalizing challenge. Here we show that a vortex-antivortex pair can be produced by a momentary electric pulse using a tip in a usual Kittel's stripe domain of a BiFeO3 thin film. Moreover, we demonstrate that the distance between the paired vortex and antivortex can be controlled by dragging the biased tip. The spatial distribution of the local piezoresponse vectors is directly mapped using angle-resolved piezoresponse force microscopy and analyzed by local winding number calculation. Our findings offer a useful concept for the control of topological defects in ferroelectrics.