Modification of Topological Surface States in Novel Mn_{1 – x}A_xBi₂Te₄/MnBi₂Te₄ (A = Si, Ge, Sn, Pb) Topological Systems

The possibility of changing the bandgap value of topological surface states in materials based on the MnBi₂Te₄ intrinsic antiferromagnetic topological insulator is investigated using ab initio calculations. These materials are produced by the substitution of nonmagnetic chemical elements (A = Si, Ge, Sn, Pb) for magnetic metal atoms (Mn) in the surface (Mn_{1 – x}A_xBi₂Te₄/MnBi₂Te₄) septuple layer. The results exhibit a s-ignificant modulation of the bandgap in a wide range from 60 meV to 0 meV with an increase in the doping level x. Moreover, it is found that the bandgap behavior depends on a dopant. Namely, a monotonic dependence of the bandgap on x is found for Si and Ge, whereas the bandgap minimum at x = 0.75 exists for Sn and Pb. The results obtained in this work suggest that the main mechanism of the bandgap modulation in the materials under study is a change in the localization of topological surface states.