Tuning band inversion symmetry of buckled III-Bi sheets by halogenation

Abstract

First-principles calculations are employed to investigate structural, electronic and topological insulating properties of XBi (X = B, Al, Ga, and In) monolayers upon halogenation. It is known that Y-XBi (X = Ga, In, Tl; Y = F, Cl, Br, I) can originate inversion-asymmetric topological insulators with large bulk band gaps. Our results suggest that Y-XBi (X = B, Al; Y = F, Cl, Br, I) may also result in nontrivial topological insulating phases. Despite the lower atomic number of B and Al, the spin-orbit coupling opens a band gap of about 400 meV in Y-XBi (X = B, Al), exhibiting an unusual electronic behavior for practical applications in spintronics. The nature of the bulk band gap and Dirac-cone edge states in their nanoribbons depends on the group-III elements and Y chemical species. They lead to a chemical tunability, giving rise to distinct band inversion symmetries and exhibiting Rashba-type spin splitting in the valence band of these systems. These findings indicate that a large family of Y-XBi sheets can exhibit nontrivial topological characteristics, by a proper tuning, and open a new possibility for viable applications at room temperature.

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

“…Figure 1 show the optimized geometrical structure of GaBi-X 2 . From the top view, the framework of Ga-Bi is DHF, which is totally different from the previous chair models [71][72][73][74][75][76][77][78], which are RHF with three-fold rotation symmetry like silicene/germanene [41,42], as shown in Figure 1 Figure 1(b)), the I atom is not right on top of a Ga atom along the z direction, but there is a little deviation between them. For the three DHF GaBi-X 2 monolayers, the optimized geometrical structure data are summarized in Table 1.…”

“…In order to tackle the above questions, we propose a new functionalization model, called distorted hexagonal framework (DHF), for iodination, bromination, and chlorination of gallium bismuth monolayer (GaBi-X 2 , X=I, Br, Cl). We find that the ground state energy of the DHF GaBi-X 2 monolayers is less than that of the RHF GaBi-X 2 monolayers, which were widely studied in previous works [71][72][73][74][75][76][77][78]. Using first-principles calculations, we investigated systematically the structure, stability and electronic property of the DHF GaBi-X 2 monolayers.…”

“…Starting from graphene [38], many kinds of QSH insulators have been predicted, including graphene with a sandwich structure [39,40], silicene (germanene/stanene) with RHF [41,42], stanene with a dumbbell structure [43][44][45], MoS 2 allotropes [46][47][48][49][50][51][52], and monolayers containing heavy metal atoms (Bi/Sb/Hf) [24,[53][54][55][56]. In the case of particular substrates [57], applying an external field [58], or using hydrogenation/functionalization [59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78], the size of those nontrivial bulk gaps can be further increased. 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.…”

“…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.…”

Chemical Vapour Deposition of sp2 Hybridised Boron Nitride

“…According to the facts mentioned above, in the current work, TEB and NH 3 were employed as boron and nitrogen precursors, respectively. Nevertheless, TEB is predicted, by the theoretical calculations, to react with NH 3 already at room temperature to form a stable adduct [114].…”