Na-functionalized IrTe2 monolayer: Suppressed charge ordering and electric field tuned topological phase transition

Abstract

Two-dimensional materials with atomic thickness usually possess superior tunability by surface adsorption than their bulk counterparts, showing great promise for novel nanotechnologies. In layered transition-metal dichalcogenide $\mathrm{Ir}{\mathrm{Te}}_{2}$ there exhibits complex structural distortions induced by charge ordering, resulting in difficulties for the applications of its corresponding monolayer material. Here, using first-principles calculations, we demonstrate that depositing Na on the surface of the $\mathrm{Ir}{\mathrm{Te}}_{2}$ monolayer can suppress the structural distortion to form a stable $\mathrm{NaIrT}{\mathrm{e}}_{2}$ sheet. It naturally breaks the inversion symmetry to enable a Rashba-type spin splitting for potential spintronic applications. In addition, the introduced empty Na $s$ band and the valence band of the $\mathrm{Ir}{\mathrm{Te}}_{2}$ monolayer can be inverted by the application of a perpendicular electric field, achieving a quantum phase transition from normal to topological insulator. Such an electric field-controlled topological phase transition is promising for the realization of topological field-effect transistors. These findings not only provide a feasible approach to stabilizing the $\mathrm{Ir}{\mathrm{Te}}_{2}$ monolayer, but also broaden its applications in spintronics and low-dissipation topoelectronics.