Stripe skyrmions and skyrmion crystals

Abstract

Skyrmions are important in quantum field theory and information technology for being topological solitons and for their attractive applications. Magnetic skyrmions are believed to be circular and stripy spin textures accompanied skyrmion crystals (SkXs) termed spiral/helical/cycloid orders have zero skyrmion number. Here we show that those stripy spin textures are skyrmions, siblings of circular skyrmions in SkXs and cousins of isolated circular skyrmions. Various irregular morphologies are the nature structures of skyrmions in the ground states. At the extreme of one skyrmion in the whole sample, the skyrmion is a ramified stripe. As the skyrmion number density increases, skyrmion shapes gradually change from ramified stripes to rectangular stripes, and eventually to circular objects. At a high skyrmion number density, SkXs are the preferred states. Our findings reveal the nature and properties of stripy spin texture, and open an avenue for manipulating skyrmions.