Three-dimensional polarization vortex configuration evolution in compressed BaTiO3/SrTiO3 superlattice

Abstract

The molecular dynamics method based on the shell model was used to investigate the polarization configuration evolution in a ferroelectric superlattice under a compressive strain that increases at a constant rate. The polarization curl was used to render the polarization configurations. The evolution of vortex domains in location, shape, and size as well as their relative movement and annihilation was observed in three dimensions. It was found that two clockwise-anticlockwise vortex arrays occur in different material layers simultaneously at a compressive strain of-0.05%. With increasing compressive strain, the vortexes continually change their locations, shapes, and sizes and possibly walk across the bimaterial interface. Their lengths could be shortened through being split in the middle or partially annihilating from both ends. Different from the single material case, there are three ways for polarization vortex annihilation to occur in ferroelectric superlattice structures. Vortexes neighboring the material interface or boundaries are inclined to annihilate first, and then the others inside the material annihilate by combining with their neighboring antivortexes. These observations are very helpful for extending applications of ferroelectric superlattices.