  In magnetic topological insulators (TIs), the interplay between magnetic
order and nontrivial topology can induce fascinating topological quantum
phenomena, such as the quantum anomalous Hall effect, chiral Majorana fermions
and axion electrodynamics. Recently, a great deal of attention has been focused
on the intrinsic magnetic TIs, where disorder effects can be eliminated to a
large extent, which is expected to facilitate the emergence of topological
quantum phenomena. In despite of intensive efforts, experimental evidence of
the topological surface states (SSs) remains elusive. Here, by combining
first-principles calculations and angle-resolved photoemission spectroscopy
(ARPES) experiments, we have revealed that EuSn2As2 is an antiferromagnetic TI
with observation of Dirac SSs consistent with our prediction. We also observe
nearly gapless Dirac SSs in antiferromagnetic TIs MnBi2nTe3n+1 (n = 1 and 2),
which were absent in previous ARPES results. These results provide clear
evidence for nontrivial topology of these intrinsic magnetic TIs. Furthermore,
we find that the topological SSs show no observable changes across the magnetic
transition within the experimental resolution, indicating that the magnetic
order has quite small effect on the topological SSs, which can be attributed to
weak hybridization between the localized magnetic moments, from either 4f or 3d
orbitals, and the topological electronic states. This provides insights for
further research that the correlations between magnetism and topological states
need to be strengthened to induce larger gaps in the topological SSs, which
will facilitate the realization of topological quantum phenomena at higher
temperatures.
