Polar antivortex in ferroelastic nanodots

Abstract

Nontrivial topological textures are significant for both scientific research and practical applications. Molecular dynamics simulations with a two-dimensional Landau potential reveal that surface relaxations generate isolated polar antivortices in mono-domain ferroelastic nanodots whose surfaces exhibit twin-boundary-like crystallographic orientation. These antivortices stem from the flexoelectric coupling between polarization and shear strain gradient induced by surface relaxations. As the nanodot size decreases, the average polarization of the antivortex first increases and then decreases, reaching a maximum value of 0.245 C/m2 at the size of 5 × 5 unit cells. Although thermal fluctuations perturb the instantaneous antivortices far below Ttr, where Ttr is the ferroelastic transition temperature of the nanodot, time-averaged dipole configurations reveal stable antivortices even near Ttr. Due to the polarization–strain-gradient coupling, bidirectional switching of the antivortex orientation can be achieved via ferroelastic domain switching, paving the way for applications in topological-based and electromechanical devices. Our findings may guide the discovery and manipulation of polar topological structures in ferroelastics, thereby broadening the range of material candidates for polar topologies.