New room-temperature 2D hexagonal topological insulator OsC: First Principle Calculations

The structural, electronic and topological characteristics of the two-dimensional (2D) binary compound OsC are investigated using DFT simulations. Phonon dispersion and molecular dynamics calculations confirm a strong structural, dynamic and thermal stability of the osmium carbide monolayer in hexagonal planar geometry where C−Os hybridization is sp2. Electronic band structures attest that OsC is a zero-gap semiconductor with the valence band coming mainly from osmium d orbitals and some contributions from carbon p orbitals. By tuning on the spin orbit coupling (SOC), the gap ΔSOC of 141 meV, corrected to 220 meV using HSE approximations, opens in the vicinity of the Γ point with the occurrence of a band inversion between d32−Os and d52−Os revealing that our system is a nontrivial QSH insulator with topological invariant Z2=1 and topological edge states. Our study shows that the room-temperature 2D topological insulator OsC is a potential material for possible applications in nanoelectronic and spintronic devices.