Quantum spin Hall effect in monolayer and bilayer TaIrTe${}_4$

Abstract

Generally, stacking two quantum spin Hall insulators gives rise to a trivial insulator. Here, based on first-principles electronic structure calculations, we confirm that monolayer TaIrTe${}_4$ is a quantum spin Hall insulator and remarkably find that bilayer TaIrTe${}_4$ is still a quantum spin Hall insulator. Theoretical analysis indicates that the covalent-like interlayer interaction in combination with the small bandgap at time-reversal invariant $\Gamma$ point results in new band inversion in bilayer TaIrTe${}_4$, namely, the emergence of quantum spin Hall phase. Meanwhile, a topological phase transition can be observed by increasing the interlayer distance in bilayer TaIrTe${}_4$. Considering that bulk TaIrTe${}_4$ is a type-II Weyl semimetal, layered TaIrTe${}_4$ thus provides an ideal platform to realize different topological phases at different dimensions.

5 pages, 7 figures