Direct imaging of the internal Bloch-components of polar-skyrmions and anti-hedgehogs in oxide heterostructures*

Emergent topological textures in ferroelectric heterostructures such as polar vortices and skyrmions has been the playground for exploring new phases and phenomena, exhibiting exotic functionalities including emergent chirality and local negative capacitance. These topologies can be realized in superlattices of (PbTiO₃)_n/(SrTiO₃)_n, either on a rigid substrate or fully lifted-off as 2D-like membranes. The electric analog of magnetic skyrmions, nm-scale polar-skyrmion bubbles, was recently observed yet their local dipole configurations and response to external stimuli are less explored. Results of electron diffraction-imaging show that the in-plane polarization curling direction is preserved (counter-clockwise, CCW) whether the skyrmion bubbles are elongated, merged, or broken apart under the perturbation of a focused electron probe. Furthermore, an ordered skyrmion square lattice appeared when heated to 373 K, in which a CCW curling dipole moment was surrounded by arrays of anti-hedgehogs and clockwise curling dipole moments.