Coexistence of Real‐ and Momentum‐Space Topology in Symmetry‐Locked Bilayer Altermagnet

ABSTRACT The integration of real‐space topological spin textures and momentum‐space topological electronic states within a single system remains challenging. However, the emergence of altermagnetism has changed this. Here, we introduce a symmetry‐locked bilayer altermagnet that concurrently hosts d ‐wave altermagnetism, momentum‐space topology, and stable antiskyrmions. In momentum‐space, it enables strain‐triggered transitions to an antiferromagnetic Weyl semimetal phase, where the Néel vector acts as a switch for spin‐layer‐polarized quantum anomalous Hall and Weyl states, alongside coupled topological states and valley polarization effects. In real‐space, the formation of interlayer co‐directional and locked in‐plane Dzyaloshinskii‐Moriya interactions facilitates the creation of coupled antiskyrmion pairs with compensated topological charges. This locking symmetry fully cancels the transverse Magnus forces, resulting in current‐driven, strictly longitudinal motion of antiskyrmions without any Hall‐like deflection. Our work establishes a symmetry‐locked bilayer altermagnetic platform for dual‐space topological magnetism and provides a theoretical route to suppressing the antiskyrmion Hall response in charge‐neutral antiskyrmions, opening pathways toward low‐power topological spintronics.