Magnon Splitting and Magnon Spin Transport in Altermagnets

Abstract Altermagnets, a new type of collinear antiferromagnet, exhibiting non-degenerate electron and magnon dispersion in momentum space have attracted intensive research attention. We theoretically analyze the origin and feature of chiral magnon splitting in representative altermagnets including tetragonal RuO2, hexagonal MnTe, and orthorhombic LaMnO3. The magnon spin transport properties including spin Seebeck and spin Nernst coefficients have been investigated. Through these materials, we demonstrate the difference of chiral splitting in d-wave and g-wave antiferromagnet on magnon transport. RuO2 with planar magnon splitting exhibits significant magnon spin Nernst and magnon spin Seebeck anisotropy in (110) and (001) planes, whereas MnTe, due to its bulk-like magnon splitting, is incapable of producing magnon spin Nernst effect. Our work may provide in-depth understanding on the mechanisms of nonrelativistic magnon splitting and thermal spin transport in altermagnets.