Understanding Atomic Scale Electronic and Physical Properties in Polar Topologies

Different polarization topologies such as vortices, skyrmions, merons, bubble domains, and flux closure domains become stable in perovskite oxide superlattices with careful interplay of elastic, electrostatic and gradient energies. Atomic scale analytical electron microscopy techniques like four-dimensional scanning transmission electron microscopy (4D-STEM), electron energy loss spectroscopy (EELS) play a crucial role to understand the formation of such unique topologies in oxides. In this talk, I will use polar vortex topology as a model system to highlight the progress that we have made to unravel their hidden electronic and physical properties. As a first example, I will explain how near-edge EELS and multiplet EELS calculations can be used to decipher atomic scale orbital hybridization in polar vortices. In the second example, I will speak about visualizing various types of chiral boundaries found in vortices using 4D-STEM. At the end of the talk, I will also talk some future challenges in this field and enlighten advantages of the upcoming electron microscopy techniques in providing right solutions.