  Recently various topological polar structures have been discovered in oxide
thin films. Despite the increasing evidence of their switchability under
electrical and/or mechanical fields, the dynamic property of isolated ones,
which is usually required for applications such as data storage, is still
absent. Here, we show the controlled nucleation and motion of isolated
three-fold vertices under an applied electric field. At the PbTiO3/SrRuO3
interface, a two-unit-cell thick SrTiO3 layer provides electrical boundary
conditions for the formation of three-fold vertices. Utilizing the SrTiO3 layer
and in situ electrical testing system, we find that isolated three-fold
vertices can move in a controllable and reversible manner with a velocity up to
~629 nm s-1. Microstructural evolution of the nucleation and propagation of
isolated three-fold vertices is further revealed by phase-field simulations.
This work demonstrates the ability to electrically manipulate isolated
three-fold vertices, shedding light on the dynamic property of isolated
topological polar structures.
