Prediction of Dirac semimetal phase with layer-resolved orbital texture in ternary tantalum nitrides

Three-dimensional topological Dirac semimetals are materials constituting a novel state of quantum matter which has attracted a lot of interest. Dirac semimetals are characterized by topologically protected double-degenerate band crossings with linear dispersion near the Fermi energy, giving rise to quasiparticles that behave like Dirac fermions. By means of first-principles calculations, we discover the Dirac semimetal phase in ternary tantalum nitrides Mg1 – x Ta2+x N3 and Li1–xTa3+xN4. The electron charge densities of the two crossing band pairs which form the Dirac nodes are located in different crystal layers in real space, thus realizing a layer-resolved orbital texture. The band inversion which leads to the Dirac points happens from the dz2 orbital from one Ta layer and dx2-y2 orbitals from another Ta layer.