2026/04/22 by Dai Q. Ho, D. Quang To, Byungkyun Kang +3 · 1 voice
Physics and Astronomy · #cond-mat.mtrl-sci
Altermagnets host momentum-selective spin splitting and chiral-split magnonic excitations despite vanishing net magnetization, enabling spin transport without ferromagnetism. In rutile structures, establishing altermagnetism spectroscopically has been challenging, motivating the search for a rutile platform with a resolvable exchange-driven chiral magnon splitting. Here we combine hybrid-functional first-principles calculations with linear spin-wave theory to show that rutile CuF2 exhibits a meV-scale splitting between magnon modes of opposite chirality along momentum directions dictated by its d-wave altermagnetic symmetry. The splitting originates from an anomalously strong long-range super-superexchange channel Cu--F⋯F--Cu, which enhances the symmetry-allowed difference between seventh-neighbour exchanges, J7b - J7a, controlling the chiral-mode splitting. We identify an orbital-resonance mechanism: energetic alignment between Cu 3dz2 and F 2pz states strengthens virtual hopping along the Cu--F⋯F--Cu path and amplifies the anisotropic long-range exchange. Rutile CuF2 therefore provides an ideal platform to validate rutile altermagnetism and suggests an orbital-energy description for engineering large chiral magnon splittings in insulating altermagnets.