| Abstract Scope |
Real-space polar topological textures like polar vortices and skyrmions emerge in ferroelectric heterostructures from the interplay of elastic, electrostatic and gradient energies. While realized in proper ferroelectric systems (e.g., PbTiO3/SrTiO3), multiferroic BiFeO3-based systems, with additional order parameters (e.g., oxygen octahedral tilts, spin) offer a largely unexplored phase space and emergent functionalities that remain to be fully understood.
To characterize these three-dimensional (3D), nanometer-sized objects, we developed advanced four-dimensional scanning transmission electron microscopy (4D-STEM) methods, enabling robust polar imaging and quantitative atomic structure determination. I will first present our discovery of a room-temperature stable, 3D dipolar wave phase in BiFeO3/TbScO3 (BFO/TSO) superlattices, detailing its unique properties and picometer-scale antiferrodistortive modes captured using multi-slice electron ptychography. I will then discuss recent advancements in non-destructive, depth-resolved polarization imaging for epitaxial thin films, opening exciting opportunities for in-situ/operando observation of topological phase transitions, paving the way for real-time control of emergent functionalities. |