We present a method to microscopically derive a small-size k⋅p Hamiltonian in a Hilbert space spanned by physically chosen ab initio spinor wave functions. Without imposing any complementary symmetry constraints, our formalism equally treats three- and two-dimensional systems and simultaneously yields the Hamiltonian parameters and the true Z2 topological invariant. We consider bulk crystals and thin films of Bi2Se3, Bi2Te3, and Sb2Te3. It turns out that the effective continuous k⋅p models with open boundary conditions often incorrectly predict the topological character of thin films.

This work was supported by the Spanish Ministry of Economy and Competitiveness MINECO (Project No. FIS2013-48286-C2-1-P) and Saint Petersburg State University (Grant No. 15.61.202.2015).

Peer reviewed