Investigation on the topological surface states of a superlattice-like magnetic topological insulator MnBi₄Te₇

The recently verified intrinsic magnetic topological insulator MnBi₂Te₄ has attracted tremendous research interest, as it is considered to be a promising platform for emergent quantum phenomena such as the quantum anomalous Hall effect, and the axion insulator state, etc. In a superlattice-like bulk of alternating MnBi₂Te₄ and Bi₂Te₃ layers, the antiferromagnetic exchanged coupling can be effectively weakened. Here, we investigate the surface states of MnBi₄Te₇ crystal via angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM) techniques. Two different band structures are observed, both showing the Dirac point located at ~280mV below the Fermi level and gapless feature at Dirac point. The two different band structures can be associated with the MnBi₂Te₄-terminated and Bi₂Te₃-terminated surfaces by STM study. We further analyze the quasi-particle interference scattering at various energies, which exhibit distinct Γ-M features corresponding to the scattering of topological surface states, showing good correspondence to ARPES data. Our results can help to understand the electronic structure and related phenomena in the emerging intrinsic magnetic topological insulators.