Chiral Split Magnon in Altermagnetic MnTe.

Altermagnetism is a newly recognized magnetic class named after the alternating spin polarizations in both real and reciprocal spaces. Like the spin splitting of electronic bands, the magnon bands in altermagnets are predicted to exhibit alternating chiral splitting. In this work, by performing inelastic neutron scattering on α-MnTe, we directly observed the altermagnetic magnon splitting. The lifted degeneracy of magnons is well explained by a symmetric-exchange origin. Further calculation based on the obtained spin-wave model demonstrates the magnons are chiral split as well. In addition, the g-wave magnetism was experimentally identified in MnTe.