IMF2017

The complex interplay of spin, charge, orbital, and lattice degrees of freedom has provided for a plethora of exotic phase and physical phenomena. Among these, in recent years, topological states of matter and spin textures have emerged as fascinating consequences of the electronic band structure and the interplay between spin and spin-orbit coupling in materials. In this lecture, I will discuss work on oxide superlattices that leverage the competition between charge, orbital, and lattice degrees of freedom. I will particularly focus on superlattices of PbTiO₃/SrTiO₃ as a model system in which we can create complex, vortex-antivortex pairs (that exhibit smoothly varying ferroelectric polarization with a 10 nm periodicity) that are reminiscent of topological features such as skyrmions and merons. The key role of a combination of advanced layer-by-layer growth techniques, atomic-resolution mapping of structure and local polar distortions using scanning-transmission electron microscopy, xray spectromicroscopy and phase-field modeling approaches will be discussed. Finally, the implications of these observations are discussed as they pertain to producing new states of matter and emergent phenomena (such as chirality) in such superlattices. I will finish up by spending some time on the broader context of oxide superlattices.