Electronic properties of La1−xTlxN systems by ab initio calculations

Electronic structures of novel La1−xTlxN rock-salt materials have been studied from first principles. The densities of states, electronic band dispersions, Fermi surface sheets, and weighted bands are analyzed. In addition, theoretical estimations of microscopic electronic properties, i.e., Fermi velocities, effective masses, charge carrier compensation ratios, and Sommerfeld coefficients are derived for these nitrides. Previously, a narrow-gap semiconducting behaviour was predicted for pure LaN. Meanwhile, our calculation results reveal a metallic character of the end compound TlN, whereas the other two La1−xTlxN systems studied appear to be semimetallic-like. Only tiny Fermi surface pockets are found for La0.5Tl0.5N. In turn, the electronic structure of La0.75Tl0.25N is similar to those of the compensated semimetallic rock-salt lanthanum monopnictides, LaSb and LaBi. Interestingly, the topologically non-trivial character of the type (1; (000)) is expected in that nitride material.