Switchable Topological Polar Textures in Freestanding Ultrathin Ferroelectric Oxides.

The rapidly expanding field of two-dimensional materials has recently extended to include freestanding complex oxides, opening new opportunities for nanoscale ferroic design. Using first-principles-based atomistic simulations, we demonstrate that ultrathin freestanding ferroelectric layers host a diverse landscape of polar states. Above a critical thickness, electrostatic confinement stabilizes a vortex-labyrinthine regime with liquid-like out-of-plane domains and long-range orientational order, which upon cooling evolves into two nearly degenerate topological configurations: a wave-helix texture and a chiral bubbles phase. Remarkably, these states are deterministically and reversibly interconverted by static and THz electric fields, enabling ultrafast electrical control of topological states. The small energy separation between the two phases creates a programmable energy landscape, establishing freestanding ferroelectric nanolayers as reconfigurable platforms for topological nanoelectronics without structural twisting or interface engineering.