Influence of the Ge-Sb sublattice atomic composition on the topological electronic properties of Ge2Sb2Te5

We present ab initio calculations of an electronic structure and a topological invariant ν0 of the Ge2Sb2Te5 compound. We have found that in the case of equiatomic composition of Ge/Sb layers the Ge2Sb2Te5 compound is the topological insulator. The ν0 invariant does not depend on a specific location of Ge and Sb atoms in the mixed layers, and depends only on their concentration. The variation of the concentration in the Ge/Sb layers leads to a change of the topological invariant of the compound.

► Bulk electronic structure of the ordered compound Ge2Sb2Te5 by full-potential linearized augmented plane wave method. ► Ge2Sb2Te5 compound turns into a topological insulator when the layers of mixed composition have equal number of Ge and Sb atoms. ► ℤ2 topological invariant does not depend on a specific location of the Ge and Sb atoms in the mixed layer. ► The ℤ2 topological invariant depends only on the concentration of the components in the Ge/Sb mixed layers. ► In a realistic Ge2Sb2Te5 crystal the disorder is not expected to affect the existence of the topological state.