Observation of switchable polar skyrmion bubbles down to the atomic layers in van der Waals ferroelectric CuInPS.

Polar skyrmions are topologically nontrivial polarization textures that demonstrate exotic physical phenomena and novel memory applications. Thus far, these textures have primarily been reported in oxide-ferroelectric-based epitaxial heterostructures because their stabilization requires an elastic energy penalty from the epitaxial strains. Here, without the epitaxial-strain engineering, we discover polar skyrmion bubbles in stand-alone van der Waals ferroelectric CuInPS crystal through the combination of piezoelectric force microscopy, high-resolution transmission electron microscopy, and phase-field simulations.