Controlling toroidal moment by means of an inhomogeneous static field: an ab initio study.

A first-principles-based approach is used to show (i) that stress-free ferroelectric nanodots under open-circuit-like electrical boundary conditions maintain a vortex structure for their local dipoles when subject to a transverse inhomogeneous static electric field, and, more importantly, (ii) that such a field leads to the solution of a fundamental and technological challenge: namely, the efficient control of the direction of the macroscopic toroidal moment. The effects responsible for such striking features are revealed and discussed.