Theoretical prediction of topological insulators in two-dimensional ternary transition metal chalcogenides (MM'X4, M = Ta, Nb, or V; M'= Ir, Rh, or Co; X = Se or Te)

Ternary transition metal chalcogenides (TTMCs) have attracted interest due to the discovery of their Weyl semimetallic property and the recent synthesis of layered TTMCs which are regarded as potential candidates for two-dimensional (2D) topological insulators. Here, employing first -principles calculations, we predicted the emergence of non-trivial band topologies in the mono -layer MM'X4 family (M= V, Nb, or Ta; M' = Co, Rh, or Ir; and X = Se or Te) within hybrid functional calculations. Five of eighteen 2D materials were found to be topological insulators, while four of them are magnetic thin films. The nontrivial topologies were verified via the calculated Z2 topological invariant and topologically protected edge states. Further calculations showed a strain-induced phase transition in VCoTe4 from a magnetic phase to a nonmagnetic topological insulating phase. Our comprehensive study revealed a diverse family of monolayer ternary transition metal chalcogenides adding new members to the current catalog of 2D topo-logical insulators and 2D magnetic materials.

Automated summary

Using first-principles calculations, non-trivial band topologies were predicted in a series of monolayer ternary transition metal chalcogenides, with some identified as topological insulators and others as magnetic thin films. Further investigations revealed a strain-induced phase transition in VCoTe4. This comprehensive study contributes new members to the current catalog of 2D topological insulators and 2D magnetic materials.