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 MnBi 2 Te 4 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 x Bi 2 Te 4 /MnBi 2 Te 4 ) 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.