Semi-Dirac electronic states in metallic layered IrSi2 compound consisting of alternate silicenes and Ir monolayers

Because silicene is very important due to its similarity to graphene, with the high Fermi velocity and Dirac cones, layered materials including silicene become very attractive for basic research and device applications. We have shown that layered IrSi₂, similar to CaSi₂ and SrSi₂, is structurally stable and investigated its electronic states by using first-principles calculations. Its z-aixs Si buckling is much larger than that in CaSi₂ and silicene, and its Si-Si-Si bond angle is much smaller than that in CaSi₂ and silicene. Our calculated results show that the layered IrSi₂ is metallic and the inter-layer conduction can be attributed to the Si p states. Furthermore, we have found a semi-Dirac electronic point at H point around the Fermi level. The semi-Dirac states will acquire a gap when the spin-orbit coupling is taken into account. These topological features should lead to some observable effects, which makes the layered IrSi₂ very attractive.