Broken Kramers' degeneracy in altermagnetic MnTe

TL;DR

This study provides direct spectroscopic evidence of altermagnetism in MnTe by observing temperature-dependent lifting of Kramers' degeneracy and spin splitting, confirming its unique electronic structure.

Contribution

The paper demonstrates the first direct experimental verification of altermagnetism through high-resolution ARPES measurements on MnTe.

Findings

Kramers' degeneracy is lifted below the magnetic transition temperature.

Spin splitting of up to 370 meV is observed.

Electronic structure changes confirm altermagnetic behavior.

Abstract

Altermagnetism is a newly identified fundamental class of magnetism with vanishing net magnetization and time-reversal symmetry broken electronic structure. Probing the unusual electronic structure with nonrelativistic spin splitting would be a direct experimental verification of altermagnetic phase. By combining high-quality film growth and $in~situ$ angle-resolved photoemission spectroscopy, we report the electronic structure of an altermagnetic candidate, $\alpha$-MnTe. Temperature dependent study reveals the lifting of Kramers{\textquoteright} degeneracy accompanied by a magnetic phase transition at $T_N=267\text{ K}$ with spin splitting of up to $370\text{ meV}$, providing direct spectroscopic evidence for altermagnetism in MnTe.