Importance of van der Waals interactions for ab initio studies of topological insulators

K. Shirali, W. A. Shelton, I. Vekhter

Published 2019-05-03Version 1

We investigate the lattice and electronic structure of the bulk and surface of the prototypical layered topological insulator Bi$_2$Se$_3$ using ab initio density functional methods. We show that inclusion of the van der Waals (vdW) interactions yields accurate values for both the lattice constants and distance between quintuple layers (basic structural units), in contrast to other standard approaches. For the topological surface state, inclusion of vdW interactions yields a Dirac cone with its tip just below the chemical potential, quasiparticle velocity very close to the experimental values, and a helical spin texture. Our results establish a framework for unified self-consistent first-principles calculations of topological insulators in bulk, slab and interface geometries, and provides the necessary first step towards ab initio modeling of topological heterostructures.