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Ferroelectric solitons crafted in epitaxial bismuth ferrite superlattices.

Vivasha GovindenPeiran TongXiangwei GuoQi ZhangSukriti MantriMohammad Moein SeyfouriSergei ProkhorenkoYousra NahasYongjun WuLaurent BellaicheTulai SunHe TianZijian HongNagarajan ValanoorDaniel Sando
Published in: Nature communications (2023)
In ferroelectrics, complex interactions among various degrees of freedom enable the condensation of topologically protected polarization textures. Known as ferroelectric solitons, these particle-like structures represent a new class of materials with promise for beyond-CMOS technologies due to their ultrafine size and sensitivity to external stimuli. Such polarization textures have scarcely been demonstrated in multiferroics. Here, we present evidence for ferroelectric solitons in (BiFeO 3 )/(SrTiO 3 ) superlattices. High-resolution piezoresponse force microscopy and Cs-corrected high-angle annular dark-field scanning transmission electron microscopy reveal a zoo of topologies, and polarization displacement mapping of planar specimens reveals center-convergent/divergent topological defects as small as 3 nm. Phase-field simulations verify that some of these structures can be classed as bimerons with a topological charge of ±1, and first-principles-based effective Hamiltonian computations show that the coexistence of such structures can lead to non-integer topological charges, a first observation in a BiFeO 3 -based system. Our results open new opportunities in multiferroic topotronics.
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