Ideal two-dimensional quantum spin Hall insulators MgA 2 Te 4 (A = Ga, In) with Rashba spin splitting and tunable properties.

For decades, topological insulators have played a pivotal role in fundamental condensed-matter physics owing to their distinctive edge states and electronic properties. Here, based on in-depth first-principles calculations, we investigate the MgA 2 Te 4 (A = Ga, In) structures belonging to the MA 2 Z 4 2D material family. Among them, the topological insulator MgGaInTe 4 exhibits band inversion and a sizeable bandgap of up to 60.8 meV which satisfies the requirement for room-temperature realization. Under the spin-orbit coupling effect, MgGaInTe 4 with inversion asymmetry undergoes Rashba spin splitting. The Rashba-like and Dirac-type edge states emerge from different terminals along (010) for MgGaInTe 4 . The external vertical electric field is verified to modulate the inverted bandgap and topological state of MgGaInTe 4 by converting a nontrivial state to a trivial state and MgIn 2 Te 4 with the original trivial state to a nontrivial one. Accordingly, MgGaInTe 4 and MgIn 2 Te 4 have significant potential for application in topological quantum field-effect transistors. Our research identifies that the MgA 2 Te 4 (A = Ga, In) structures have huge potential to be candidate 2D materials for spintronics and topological quantum devices.