Dirac Cones in Two-Dimensional Lattices: Janugraphene and Chlorographene

Using density functional theory, we predict that two supposedly ordinary two-dimensional materials, janugraphene and chlorographene, feature Dirac points in their band structure even though they possess nonequivalent bonds and rectangular lattices. Our results provide a new perspective on the formation of Dirac points since the honeycomb structure composed of two equivalent sublattices and hexagonal symmetry are commonly considered to be necessary preconditions for the presence of Dirac points in two-dimensional materials. The Dirac fermions of these materials are rather robust in response to external electric field. Furthermore, the possible underlying physical mechanisms are discussed in detail. We envision that janugraphene and chlorographene will greatly broaden the scientific and technological impact of two-dimensional Dirac semimetals.