Topological Insulating Phases in Two-Dimensional Bismuth-Containing Single Layers Preserved by Hydrogenation

Abstract

<img src="http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2015/jpccck.2015.119.issue-41/acs.jpcc.5b07961/20151009/images/medium/jp-2015-07961p_0007.gif" /> Two-dimensional (2D) binary XBi compounds, where X belongs to group III elements (B, Al, Ga, and In), in a buckled honeycomb structure may originate sizable gap Z2 topological insulators (TIs). These are characterized by exhibiting single band inversion at the Γ point as well as nontrivial edge states in their corresponding nanoribbons. By using first-principles calculations, we demonstrate that hydrogenation of XBi single layers leads to distinct and stable crystal structures, which can preserve their topological insulating properties. Moreover, hydrogenation opens a band gap in this new class of 2D Z2 TIs, with distinct intensities, exhibiting an interesting electronic behavior for viable room-temperature applications of these 2D materials. The nature of the global band gap (direct or indirect) and topological insulating properties depend on the X element type and spatial configuration of the sheet, as well as the applied strain. Our results indicate that the geometric configuration can be crucial for preserving totally the topological characteristics of the hydrogenated sheets. We identify sizable band inversions in the band structure for the relaxed hydrogenated GaBi and InBi in their chairlike configurations and for hydrogenated BBi and AlBi under strain. Based on these findings, hydrogenation gives rise to a flexible chemical tunability and can preserve the band topology of the pristine XBi phases

Single and bilayer bismuthene: Stability at high temperature and mechanical and electronic properties

“…This trend agrees with present findings. Band gap values calculated by Freitas et al [30] using PBE with and without SOC agree with the present values.…”

“…The effects of strain and electric field on the electronic structure of a single-layer A7 structure are investigated to show that the structure is a robust 2D topological insulator against strain and electrical field [27]. In addition, the electronic properties of XBi binary compound (X = B, Al, Ga, and In) and hydrogenated Bi(111) films [30] have been explored within the perspective of topological insulator.…”

Modification of electronic structure, magnetic structure, and topological phase of bismuthene by point defects

“…Furthermore, the topological insulator property has remained robust under an applied electric field and strain [15]. Not only bare surfaces of Bi, but also the surfaces covered with H have been studied to reveal the effect of adsorbed hydrogen on the topological character of the material [17].…”

Gallium bismuth halide GaBi-X2 (X = I, Br, Cl) monolayers with distorted hexagonal framework: Novel room-temperature quantum spin Hall insulators

“…Currently, the largest nontrivial bulk gap is 1.08eV found in Bi 2 F 2 monolayer [59,60], which shows that chemical functionalization is a very powerful way to obtain a large nontrivial bulk gap. Using first-principles calculations, some group III-V monolayers were predicted to be QSH insulators with a large bulk gap [24] and it was found that this gap can be enlarged via hydrogenation/functionalization [71][72][73][74][75][76][77][78]. After functionalization, their structures can all be regarded as being composed of RHF.…”