Abstract
Nontrivial topological structures offer a rich playground in condensed matters and promise alternative device configurations for post-Moore electronics. While recently a number of polar topologies have been discovered in confined ferroelectric PbTiO3 within artificially engineered PbTiO3/SrTiO3 superlattices, little attention was paid to possible topological polar structures in SrTiO3. Here we successfully create previously unrealized polar antivortices within the SrTiO3 of PbTiO3/SrTiO3 superlattices, accomplished by carefully engineering their thicknesses guided by phase-field simulation. Field- and thermal-induced Kosterlitz–Thouless-like topological phase transitions have also been demonstrated, and it was discovered that the driving force for antivortex formation is electrostatic instead of elastic. This work completes an important missing link in polar topologies, expands the reaches of topological structures, and offers insight into searching and manipulating polar textures.
Highlights
Nontrivial topological structures offer a rich playground in condensed matters and promise alternative device configurations for post-Moore electronics
Creating topologies in polar systems is usually more difficult as the dielectric anisotropy in polar materials is much stronger than magnetic ones[1], and there is tremendous energy penalty when polarization rotates to form polar topologies
Based on systematic phase-field simulations, we have identified four typical polar configurations (Fig. 1b–e) for (PTO)n/(STO)m, enabling us to construct a phase diagram to guide the design (Fig. 1f)
Summary
It suggests that the formation of antivortex in STO is largely driven by electric field, while misfit strain in superlattice plays a negligible role This is in sharp contrast to corresponding analysis for PTO (Supplementary Fig. 10) showing that elastic energy is negative while electric energy is positive, so that the driving force for vortex formation in PTO is elastic, as commonly understood. The field induced phase transition renders dielectric hysteresis as shown in Fig. 4d, where dielectric tunability as large as 50.7% is observed
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