Emergent Gauge Fields and Linear Dichroism in Spin-Textured Altermagnets

Spin textures are ubiquitous in antiferromagnets, yet their consequences for altermagnets remain largely unexplored. We show that smooth spatial variations of the Néel order act on itinerant electrons as emergent gauge fields that couple to the altermagnetic sublattice-odd channel. For a coplanar spin helix, this channel generates two responses that vanish when it is removed: a momentum-resolved sublattice-odd spectral structure and a net interband linear dichroism whose principal axes are controlled by the helix wave vector, so the optical response can be steered by the magnetic texture. The dichroism exhibits two distinct regimes separated by a crossover: at low frequencies the absorption axis is locked to the crystal axes, while at high frequencies it tracks the helix. Anisotropic dc transport provides a complementary quantitative signature, and all signatures are robust to weak intrinsic spin-orbit coupling. Our results identify polarization-resolved optics and sublattice-sensitive spectroscopy as direct probes of textured altermagnetic states and suggest a route to direction-selective electronic and optical functionality in altermagnets.