High mobility of isolated three-fold polar vertices by electric fields

Recently various topological polar structures have been discovered in oxide thin films. Despite the increasing evidence of their switchability under electrical or mechanical fields, the dynamic property of an isolated one, which is usually required for applications such as data storage, is still absent as they are always formed as arrays in thin films and evolve together due to strong interactions with their neighbors. Here, we show the controlled nucleation and high mobility of isolated three-fold vertices under an applied electric field. At PbTiO3/SrRuO3 interfaces, nanosized three-fold vertices are formed. A two-unit-cell thick SrTiO3 layer provides critical electrical boundary conditions for the formation of three-fold vertices. Utilizing the SrTiO3 layer and in situ TEM electrical testing system, we found isolated three-fold vertices can move a long distance along the interface under electric fields in a controllable and reversible manner. Microstructural evolution details of the nucleation and propagation of isolated three-fold vertices are further revealed by phase-field simulations. This work demonstrates the high mobility of isolated three-fold vertices, shedding light on the extraordinary dynamic properties of isolated topological polar structures.