Polar vortex hidden in twisted bilayers of paraelectric SrTiO<sub>3</sub>.

Sha, Haozhi; Zhang, Yixuan; Ma, Yunpeng; Li, Wei; Yang, Wenfeng; Cui, Jizhe; Li, Qian; Huang, Houbing et al. · Nat Commun · 2024

basic_science · Level V

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Abstract

Polar topologies, such as vortex and skyrmion, have attracted significant interest due to their unique physical properties and promising applications in high-density memory devices. To date, all known polar vortices are present in or induced by ferroelectric materials. In this study, we find polar vortex arrays in paraelectric SrTiO<sub>3</sub>. Using multislice electron ptychography, the evolution of vorticity along the vortex axis is revealed in twisted bilayers of SrTiO<sub>3</sub> with deep-sub-angstrom resolution and one picometer accuracy. The surprising finding of polar vortices in a paraelectric crystal opens up opportunities for polarization physics and corresponding new devices.