Modification of Topological Surface States in Novel Mn1 – xAxBi2Te4/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 (Mn1 – xAxBi2Te4/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.