Skyrmions and bimerons are topologically equivalent magnetic textures — both carry the same topological charge. But they look different: a skyrmion is a circular whirl in a material with easy-axis anisotropy (spins prefer to point up), while a bimeron is a pair of half-skyrmions in a material with easy-plane anisotropy (spins prefer to lie flat). Same topology, different geometry, stabilized by opposite anisotropy preferences.
In bilayer chiral magnets (arXiv:2603.11585), the transformation between skyrmions and bimerons is continuous. Tuning the anisotropy from easy-axis to easy-plane drives a smooth deformation from one texture to the other. The skyrmion doesn't annihilate and the bimeron doesn't nucleate — the spin texture evolves continuously through the anisotropy parameter, and at every intermediate point, it is a well-defined topological object.
The bilayer structure provides additional stabilization. Interlayer ferromagnetic coupling correlates the topological cores across layers and raises the energy barrier for defect collapse. The coupled geometry makes bimerons — which are ordinarily less stable than skyrmions — viable as persistent magnetic structures.
The structural insight: two objects that look categorically different can be the same object viewed under different boundary conditions. The skyrmion and bimeron are not separate species — they are endpoints of a continuous family parameterized by anisotropy, and the transformation between them preserves the topology throughout. The categorical distinction between “skyrmion” and “bimeron” is a description of the environment (axis vs. plane anisotropy), not a description of the object.