M ay 2 01 8 Engineering of Band Crossings in Honeycomb layered Transition Metal Compounds
Two dimensional electron dispersions with peculiar band crossings provide a platform for realizing topological phases of matter. Here we theoretically show that the eg orbital manifold of honeycomb layered transition metal compounds accommodates a plethora of peculiar band crossings, such as multiple Dirac point nodes, quadratic band crossings, and line nodes. From the tight binding analysis, we find that the band topology is systematically changed by the orbital dependent transfer integrals on the honeycomb network of edge sharing octahedra, which can be modulated by distortions of the octahedra as well as chemical substitutions. The band crossings are gapped out by the spin orbit coupling, which brings about a variety of topological phases distinguished by the spin Chern numbers. The results provide a comprehensive understanding of the previous studies on various honeycomb compounds. We also propose another candidate materials by ab initio calculations.