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.
Highlights
Non-trivial textures of vector order parameters in real, momentum, and complex-phase spaces form the basis for exotic phenomena.[1]
The two-dimensional (2D) winding number is invariant under continuous deformation and the total topological charge is protected by the given boundary condition.[1,8]
Modifying the overall topological structure requires a great deal of energy depending on the size of the system, so that no modulation of the topological charge is achieved in an infinite-sized uniform sample
Summary
Non-trivial textures of vector order parameters in real, momentum, and complex-phase spaces form the basis for exotic phenomena.[1]. We demonstrate the creation of a single vortex–antivortex pair in ferroelectrics and the separation of the pair through tip-induced electric fields in a topologically trivial ferroelectric thin film of BiFeO3 (BFO) deposited with a bottom electrode SrRuO3 (SRO) on a (110)O-oriented DyScO3 (DSO) substrate (where the subscript “O” represents the orthorhombic index).[23] We clarify the detailed texture of the topologically excited pair with the aid of angle-resolved lateral piezoresponse force microscopy (PFM).[24,25,26] we analyze the map of experimentally measured piezoresponse vectors by calculating local winding numbers to identify the exact locations of the nontrivial topological charges.
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