Observation of room temperature polar bubbles/ skyrmions in oxide heterostructures*

The complex non-collinear and non-coplanar topological textures in complex oxides have recently attracted of their various exotic phenomena (such as emergent structural chirality). Among them the recent discovery of polarization vortices with toroidal order in superlattices of (PbTiO₃)_n/(SrTiO₃)_n [1]. Topologically protected nanometric polar vortices, skyrmions are being are rarely investigated in complex heterostructures. Here, we describe that for a room-temperature polar bubbles/skyrmions with 6-7 nm size in PbTiO₃/SrTiO₃ heterostructures via real space imaging transmission electron microscopy, phase field simulations and ab-initio calculations. Phase-field and ab-initio studies have revealed the presence of this new polarization topology of ferroelectric bubbles/skyrmions that arise from a combination of epitaxial strain and layer thickness. This finding of nanometre-scale polar topology in a thin film may be useful as a fertile ground for promising applications.

[1] Yadav, A. K. et al. Observation of polar vortices in oxide superlattices. Nature 530, 198-201 (2016).