First-principles investigation of two-dimensional topological insulators BiX (X=H, F, O)

Abstract

In order to exploit the nontrivial topological phase of matter for realizing room temperature transport applications, two-dimensional (2D) topological insulators (TIs) with large bulk band gaps are necessary. Based on first-principles calculations, the electronic and topological properties of 2D large gap TIs BiX (X = H, F, O) have been thoroughly investigated. We confirmed their nontrivial topological nature by calculating topological invariant (using Fu-Kane method) and observed odd number pairs of topologically protected gapless edge states from band structures of their zigzag nanoribbons. The strong spin–orbit coupling effect arising from heavy bismuth atoms not only affects the electronic structures, but also obviously influences the structural parameters such as lattice constant, bond length and buckling height. The key role of orbital filtering effect of X atoms in the electronic and topological properties has been illustrated by employing atomic-orbital-resolved band structures. Furthermore, we proposed a large band gap substrate, hexagonal boron nitride (h-BN), in a BiF/h-BN heterostructure, in which the h-BN substrate preserves the nontrivial topological behavior of BiF. To the best of our knowledge, BiF/h-BN with the gap of 1.041 eV has the largest band gap among all previously studied TI/substrate heterostructures. These findings make this structure a promising platform for high temperature low-dissipation spintronic nanodevices.