Axial hypertoroidal moment in a ferroelectric nanotorus: A way to switch local polarization

Growth of ferroelectric nanotori is reported and first-principles-based effective Hamiltonian simulations were performed on these new objects. They could reproduce the nonpolar (phase I) and homogeneously toroidized (phase II) states of an isolated nanotorus. Computation of an axial hypertoroidal moment leads to numerical observation of two new phases: (i) a homogeneously hypertoroidized one (phase III) that can be switched by a homogeneous electric field and (ii) another one with striking newpolarization patterns (phase IV) due to azimuthal variations of the hypertoroidal moment. In both phases, hypertoroidization coexists with a homogeneous axial toroidal moment.