Electric Configuration of the Topological Textures in a Ferroelectric Nanoplate by Partial Domain Switching

Vortices in ferroic materials have not only provided a new perspective for describing collective orders in matter but also given potential applications for high density non-volatile information storage. However, creation of stable isolate ferroelectric vortex states and electric configuration of the topological invariant in dielectrics are experimentally still veiled. Here, we show an epitaxial ferroelectric square nanoplate of bismuth ferrite subject to a large strain gradient associated with misfit strain relaxation enables five discrete levels for the ferroelectric topological invariant of the entire system as a consequence of the peculiar radial strain relaxation and the domain wall chirality. The total winding number of the nanoplate can be configured from -1 to 3 by selective non-local electric switching of the radial-quadrant domains. By using position-sensitive angle-resolved piezoresponse force microscopy, we directly identify the existence of vortices and anti-vortices, observe pair creation and annihilation, and manipulate the total net number of vortices. Our findings offer a useful concept to stabilize and control the ferroelectric vortices for multi-level topological defect memory.