Modulation of the Dirac Point Band Gap in the Antiferromagnetic Topological Insulator MnBi 2 Te 4 due to the Surface Potential Gradient Change

The possibility of significant modulation of the band gap open at the Dirac point (DP) in the range from 15 to 55 meV for different samples of the antiferromagnetic topological insulator MnBi 2 Te 4 is shown using angle-resolved photoemission spectroscopy. The density functional theory is used to analyze the relation between the gap at the DP and the surface potential gradient, the change of which is modeled by the application of an electric field normal to the (0001) MnBi 2 Te 4 surface. The possibility of both decreasing and increasing the DP gap in the range from 5 to 89 meV with respect to the initial value of 81 meV due to the application of a field is shown. When a field is applied, the localization of topological surface states and the magnetic moments of surface atoms change. Our analysis demonstrates the possibility of an artificial band gap modulation at the DP over a wide energy range, which can be used to modulate the magnetoelectric properties of MnBi 2 Te 4 -based systems in applied research and problems.