Highly Responsive Polar Vortices in All-Ferroelectric Heterostructures

P Kavle and AM Ross and KP Harikrishnan and P Meisenheimer and A Dasgupta and JY Yang and CC Lin and H Pan and P Behera and E Parsonnet and XX Huang and JA Zorn and YT Shao and S Das and S Liu and DA Muller and R Ramesh and LQ Chen and LW Martin, ADVANCED MATERIALS, 36 (2024).

DOI: 10.1002/adma.202410146

The discovery of polar vortices and skyrmions in ferroelectric- dielectric superlattices such as (PbTiO3)n/(SrTiO3)n has ushered in an era of novel dipolar topologies and corresponding emergent phenomena. The key to creating such emergent features has generally been considered to be related to counterpoising strongly polar and non-polar materials thus creating the appropriate boundary conditions. This limits the utility these materials can have, however, by rendering (effectively) half of the structure unresponsive to applied stimuli. Here, using advanced thin-film deposition and an array of characterization and simulation approaches, polar vortices are realized in all-ferroelectric trilayers, multilayers, and superlattices built from the fundamental building block of (PbTiO3)n/(PbxSr1-xTiO3)n wherein in-plane ferroelectric polarization in the PbxSr1-xTiO3 provides the appropriate boundary conditions. These superlattices exhibit substantially enhanced electromechanical and ferroelectric responses in the out-of-plane direction that arise from the ability of the polarization in both layers to rotate to the out-of-plane direction under field. In the in-plane direction, the layers are found to be strongly coupled during switching and when heterostructured with ferroelectric-dielectric building blocks, it is possible to produce multistate switching. This approach expands the realm of systems supporting emergent dipolar texture formation and does so with entirely ferroelectric materials thus greatly improving their responses.

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