Origin of Dirac Cones in SiC Silagraphene: A Combined Density Functional and Tight-Binding Study

Abstract

The formation of Dirac cones in electronic band structures via isomorphous transformation is demonstrated in 2D planar SiC sheets. Our combined density functional and tight-binding calculations show that 2D SiC featuring C–C and Si–Si atom pairs possesses Dirac cones (DCs), whereas an alternative arrangement of C and Si leads to a finite band gap. The origin of Dirac points is attributed to bare interactions between Si–Si bonding states (valence bands, VBs) and C–C antibonding states (conduction bands, CBs), while the VB–CB coupling opens up band gaps elsewhere. A mechanism of atom pair coupling is proposed, and the conditions required for DC formation are discussed, enabling one to design a class of 2D binary Dirac fermion systems on the basis of DF calculations solely for pure and alternative binary structures