Giant spin–orbit coupling topological insulator h-Ga ₂ Bi ₂ with exotic O-bridge states

The two-dimensional (2D) topological insulator (TI) is a promising material for designing dissipationless spintronic devices. Although many candidates have been found, few of them have a massive spin–orbit coupling (SOC) strength with high stability. In the present work, we demonstrate that h-Ga2Bi2 is a highly stable 2D TI with a massive Eg(Γ) at the Γ point of 1.477 eV, while the global band gap is 0.20 eV, which is sufficiently large for room temperature (∼26 meV). The edge states are greatly affected by the geometrical configuration of ribbon edges. The linear dispersive edge states still hold when the nanoribbon is limited to 1.7 nm, which actually realizes the ideal nanowire as theoretically derived in the field of TI. Most excitingly, an exotic ‘O-atom bridge’ is proposed here, and resides in the inner part of the nanoribbon, and so is thus highly protected from damage. The corresponding ‘O-bridge states’ display the interaction of electrons in a clear pattern, which leads to a better understanding of the 2D TI.