We performed angle-resolved photoemission spectroscopy (ARPES) on hexagonal MnTe, a candidate for an altermagnet with a high critical temperature (TN=307 K). By utilizing photon-energy-tunable ARPES in combination with first-principles calculations, we found that the band structure in the antiferromagnetic phase exhibits a strongly anisotropic band-splitting associated with the time-reversal-symmetry breaking, providing the first direct experimental evidence for the altermagnetic band-splitting. The magnitude of the splitting reaches 0.8 eV at non-high-symmetry momentum points, which is much larger than the spin-orbit gap of ~0.3 eV along the GK high-symmetry cut. The present result paves the pathway toward realizing exotic physical properties associated with the altermagnetic spin-splitting.
@article{arxiv.2308.10117,
title = {Observation of Giant Band Splitting in Altermagnetic MnTe},
author = {T. Osumi and S. Souma and T. Aoyama and K. Yamauchi and A. Honma and K. Nakayama and T. Takahashi and K. Ohgushi and T. Sato},
journal= {arXiv preprint arXiv:2308.10117},
year = {2024}
}