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 BiFeO 3 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.

Creating polar antivortex in PbTiO3/SrTiO3 superlattice

“…2i ) directions show that out-of-plane ( D z ) and in-plane ( D x ) polar vectors reverse their directions when passing through the antivortex core, approaching and departing the core from two sets of opposite directions (head-to-head and tail-to-tail) 26 , 28 , 30 , 33 . Using the experimental data, we also obtain the distribution of winding numbers 34 (Supplementary Fig. 5a ), confirming the topological nature of vortices and antivortices about their respective cores, where two antivortices with winding number −1 between four vortices with winding number 1 are revealed.…”

“…We carried out a local winding number analysis for polar angle distribution in order to authenticate the topological nature of vortices and antivortices about their respective cores. The two-dimensional winding number n along a closed loop C was calculated by the following line integral , where ∇ θ is the angle gradient of polarization vectors along the integral loop C 30 , 34 , 39 . By performing a local winding number calculation on each closed loop, we are able to identify the existence of a single vortex and antivortex that gives a winding number equal to +1 and −1, respectively (for illustration simultaneously observe Figs.…”

Giant Thermal Transport Tuning at a Metal/Ferroelectric Interface

“…Thus, the polarization state of each point in the overlapping area was determined by the polarization and phase shift of the fitting curve. [30] Then 360° was divided into eight directions uniformly (each one occupied 45°, according to the polarization of BFO) and the in-plane polarization direction was classified. The polarizations were represented by different colors, the final treated polarization diagrams are shown in Figure 2c.…”

Enhanced energy storage performance and thermal stability in relaxor ferroelectric (1‐x)BiFeO3‐x(0.85BaTiO3‐0.15Bi(Sn0.5Zn0.5)O3) ceramics

“…Lead‐free dielectrics such as BaTiO 3 , (Bi,Na)TiO 3 , (K,Na)NbO 3 , and BiFeO 3 (BF)‐based systems have thus been extensively investigated 16‐24 . Among these perovskite oxide dielectrics, BF has been considered as a very promising alternative to replace lead‐free materials, due to its super large ferroelectric polarization (≈90 μC/cm 2 ) 25 . However, BF has some intrinsic disadvantages, such as the high electric leakage, and large hysteresis loop, limiting its application in energy storage 17 …”

“…[16][17][18][19][20][21][22][23][24] Among these perovskite oxide dielectrics, BF has been considered as a very promising alternative to replace lead-free materials, due to its super large ferroelectric polarization (≈90 μC/ cm 2 ). 25 However, BF has some intrinsic disadvantages, such as the high electric leakage, and large hysteresis loop, limiting its application in energy storage. 17 It is well known that large P max , small P r , and high dielectric breakdown strength (E b ) are necessary for high density energy storage.…”