DFT-based Engineering of Dirac Surface States in Topological-insulator Multilayers

A highly insulating bulk state and a tunable Dirac cone surface state are required for future spintronics device applications of spin-polarized surface states in three-dimensional topological insulators. Here, a slab model with heterostructural Bi2Se3-related quintuple layers is employed to conduct first-principles simulations. The computational results show that the Dirac-point energy can be optimally tuned by the selection of an appropriate pair of materials, so that the work function of the surface quintuple layer is slightly different from that of the inner quintuple layers. The ideal surface state is obtained in a Bi2Te3/(Bi2Te2Se)4/Bi2Te3 slab, in which the Fermi lines show a significant warping effect and both in-plane and out-of-plane components of spin polarization emerge.