Predicting multiple Dirac-cones and ultrahigh Fermi velocity in perovskite R(3)over-barc phase LaCuO3

摘要

Three-dimensional (3D) Dirac semimetal as an intermediate between a trivial insulator and topological insulator has generated much attention, yet there are currently very few experimental studies. In this study, on the basis of density functional theory calculations and a theoretical tight-binding model, we have predicted that the experimentally synthesised LaCuO3 compound (R% 3c phase) possesses multiple Dirac cones in its electronic structure. The bands are linearly dispersed, and the compound exhibits comparable Fermi velocity (0.92 x 10(6) m s(-1)) to that of graphene; also, the bands possess large regions of linear dispersion. More interestingly, rings of Dirac nodes formed by multiple Dirac points and a distorted Dirac cone coexist in the LaCuO3 compound. The Dirac states in LaCuO3 are protected by the D3d symmetry, with dominant contributions from the d orbitals of Cu and p orbital of O. The particular space groups allow 3D Dirac points as symmetry-protected degeneracies. Thus, there are probably numerous 3D Dirac semimetals in the perovskite (R% 3c) phase yet to be discovered.