The existence of fractionally quantized topological corner states serves as a
key indicator for two-dimensional second-order topological insulators (SOTIs),
yet has not been experimentally observed in realistic materials. Here, based on
first-principles calculations and symmetry arguments, we propose a strategy for
achieving SOTI phases with in-gap corner states in
(MnBi2βTe4β)(Bi2βTe3β)mβ films with antiferromagnetic (AFM) order.
Starting from the prototypical AFM MnBi2βTe4β bilayer, we show by an
effective lattice model that such SOTI phase originate from the interplay
between intrinsic spin-orbital coupling and interlayer AFM exchange
interactions. Furthermore, we demonstrate that the nontrivial corner states are
linked to rotation topological invariants under three-fold rotation symmetry
C3β, resulting in C3β-symmetric SOTIs with corner charges fractionally
quantized to 3nββ£eβ£ (mod e). Due to the great recent
achievements in (MnBi2βTe4β)(Bi2βTe3β)mβ systems, our results
providing reliable material candidates for experimentally accessible AFM
higher-order band topology would draw intense attentions.Comment: 6 pages, 4 figure