Anisotropic Spin Transport Enhanced by Zero-Dimensional Weyl Nodes in Altermagnetic Weyl Semimetals

The altermagnetic phase is a newly discovered magnetic state, distinguished by a collinear compensated spin configuration, which fundamentally deviates from traditional antiferromagnetic ordering. In this study, a novel topological altermagnet is introduced featuring a distinctive altermagnetic ordering and multiple zero-dimensional (0D) Weyl nodes, thereby defining it as an altermagnetic Weyl semimetal. Using Mn₄(PO₄)₃ crystal (magnetic space group 122.337) as a case study, it is discovered that its altermagnetic configuration reveals two distinct spin channels accompanied by pronounced transport anisotropy. Crucially, the symmetry-protected Weyl points (WPs) endowed with quantized topological charges bolster the anisotropic spin transport, with the chiral topology of WPs ensuring robust spin-momentum locking. Uniquely, this altermagnetic Weyl semimetal generates spin-selective surface arc states via chiral polarization of WPs, a distinctive feature absent in antiferromagnetic Weyl analogues. The research not only aids in comprehending interplay between altermagnetism and topological states, but also offers a material plateau for the design of energy-efficient topological spintronic devices.