BaCo_1-xNi_xS₂ is a quasi-2D Mott system, where electron doping drives the antiferromagnetic and insulating phase at x=0 to a metallic and paramagnetic one at the critical value x_cr = 0.22 [1]. ARPES measurements on high-quality single crystals of BaNiS₂ and band structure calculations suggest a moderate renormalization effect due to weak electronic correlations and a large Rashba coupling amplified by a huge staggered crystal field [2]. ARPES and Quantum Oscillation measurements allowed to propose the first experimental Fermi surface in which a 3D Dirac cone, presumably symmetry protected, emerged in middle of GM direction [3].
In this context, we measured the optical conductivity on the ab-plane of the highly conducting BaNiS₂ at various temperatures. These actually indicated a large thermal evolution with an unconventional linear behavior in the optical conductivity versus the wavenumber, recently explained and observed in 3D Dirac semimetal [4, 5]. A comparative study of the optical conductivity experimental and simulated from ab initio calculations including a Hubbard repulsion term, U will be discuss in order to understand the role of the 3D Dirac cone in optical conductivity of BaNiS₂.