Possibility of topological properties in 2D cadmium chalcogenide (CdX, X = S, Se, and Te) buckled honeycomb monolayer on substitutional doping

Two-dimensional honeycomb monolayers doped with tin atoms are designed from (111) surface of bulk zinc blende structures of cadmium chalcogenides using first principles density functional theory based calculations. On relaxation the buckled honeycomb monolayer shows signature of band inversion between Sn and Cd orbital at the zone center (Γ point) deep in the valence band and high above in the conduction band. The band inversion, due to hybridization, stays even after inclusion of spin-orbit coupling. The systems were chosen with an intention to exploit the possibility of d-d band inversion. CdSnS has s-s band inversion but CdSnSe and CdSnTe monolayers do show band inversion involving d states. The calculated phonon spectra confirmed the stability of all the systems studied. The details of the electronic structure bring out the importance of s-d band inversion. We also report the topological invariants and analysis of edge state properties and band structure of these materials in ribbon geometry. Such systems can be useful for technological application in the Spintronic domain.