Towards phase field models of skyrmions and multiferroic domains

Abstract:
In this talk, I will highlight work done at FZU in the past year regarding the topic of constructing mesoscopic models of ferroelectric and multiferroic materials and the subsequent search for stable skyrmions in their nanostructures. One goal of our group has been to investigate the domain structure of the multiferroic skyrmion-lattice host GaV4(S,Se)8. Using density-functional methods, we probe the order parameter subspace of GaV4Se8 and parameterize an effective thermodynamic potential useful for domain topology prediction. Additionally for multiferroic BiFeO3, we also demonstrate that once the energy landscape has been thoroughly explored as was done previously by co-workers, that domain wall profiles can be predicted in agreement with previously published DFT results. In parallel to this effort, the search for skyrmion and skyrmion-like phases in ferroelectric nanoparticles continues. Here, the phase field method is used to explored confined ferroic phases of varying nanoshapes of lead titanate embedded in dielectric media. It is shown that the directionality of an intrinsic vortex-like core can be controlled using an applied electric field or tunable interparticle spacings, and that the arrival of a skyrmion-like vortex phase is universal across the entire superellipsoid shape morphology.