Evolution of the electronic structures of magnetic topological insulator MnBi2Te4 film and bulk

Intrinsic magnetic topological insulator MnBi₂Te₄, after been exfoliated to atomically thin film and electrostatically gated, exhibits rich and fascinating quantum properties such as quantum anomalous Hall effect and axion insulator state. However, despite these great breakthroughs, there are still many mysteries in the electronic structure of MnBi₂Te₄ to be understood. First of all, the topological surface states (TSSs) were observed by angle-resolved photoemission spectroscopy (ARPES) only at low photon-energies and exhibit a diminishing energy gap that is immune to the magnetic transition, in drastic contrast to the theoretical prediction and transport measurements. Secondly, the dispersion of TSSs shows a kink-like structure and is strongly broadened near the Fermi level (EF), which is out of the expectation of Fermi liquid theory. Thirdly and also importantly, although the intriguing transport properties are realized in MnBi₂Te₄ thin films, their electronic structure is not sufficiently investigated by experiments and seems to be in drastic contrast to that of bulk material. In this talk, we will show our ARPES studies on the electronic structure of MnBi₂Te₄ film as well as its evolution with temperature, film thickness, and surface doping of alkali metals. A trivial surface band is induced by surface doping which may hold the key to understand the peculiar dispersion of the topological surface states in MnBi2Te4. Our results will shed light on the understanding of the electronic structure and intriguing transport properties of the system.