Topological Electronic Structure and Its Temperature Evolution in Antiferromagnetic Topological Insulators

Magnetic topological insulators represent a novel state of topological quantum materials with unique blends of non-trivial band topology and magnetism. Recently, Intrinsic magnetic topological insulator MnBi₂Te₄ is shown to exhibit rich topological effects such as quantum anomalous Hall effect and axion electrodynamics, which attracts tremendous research interests. Here, we carried out comprehensive and high-resolution angle-resolved photoemission spectroscopy studies on MnBi₂Te₄, and identified its topological electronic structure. In contrast to theoretical predictions and previous studies, we observe topological surface states with a diminished gap forming a characteristic Dirac cone. In addition, the temperature evolution of the energy bands reveals their interplay with the magnetic phase transition by showing interesting differences between the bulk and surface states, respectively. Our results provide important insights into not only the exotic properties of MnBi₂Te₄, but also the generic understanding of the interplay between magnetism and topological electronic structure in magnetic TQMs.