Topological structures in ferroelectric nanodots revealed from first-principles simulations

Ferroelectric materials are known to exhibit spontaneous polarization [1]. The behavior of bulk ferroelectrics is well understood. However, these materials exhibit unusual characteristics like topological vortices as their dimensionality decreases [2-4]. Using an effective Hamiltonian approach, we computationally investigate BaTiO3 (BTO) nanodots of various sizes ranging from 12nm to 40nm to study the vortex dipole patterns in 3D. The simulation is carried out at a temperature of 10K in the rhombohedral phase of BTO. Our analysis predicts the existence of multiple vortices in different cross-sections of the nanodot and the number of vortices present increases with dot size. The trajectory of the principal vortex in different cross sections is found to be along the diagonal of the dot. Furthermore, applying a DC electric field ranging from 0 to 2000kV/cm in steps of 200kV/cm annihilates the vortex at 1400kV/cm to introduce a homogenous pattern. Our findings offer new insights into low-dimensional ferroelectrics and can find potential applications in novel nanoelectronic devices.