Chiral altermagnon in MnTe

Altermagnetism has been recognized as a magnetic phase that bridges the properties of ferro- and antiferromagnetism. The momentum-dependent spin splitting observed in these materials reflects their distinctive symmetry characteristics, which also establish the conditions for chiral magnons to emerge. Here we provide direct experimental evidence for a chiral magnon in the altermagnetic candidate manganese telluride (MnTe) revealed by circular-dichroism resonant inelastic x-ray scattering. This mode, which we term chiral altermagnon, exhibits a distinct momentum dependence of its spin polarization consistent with the altermagnetic g -wave symmetry of MnTe. Our polarization-resolved data corroborate the existence of a discrete class of magnetic excitations, demonstrating how altermagnetic order shapes spin dynamics and paving the way for advances in spintronic and quantum technologies.