Type: Article
Publication Date: 2021-11-29
Citations: 8
DOI: https://doi.org/10.1103/physrevb.104.l201115
We investigate the optical conductivity and far-infrared magneto-optical response of ${\mathrm{BaNiS}}_{2}$, a simple square-lattice semimetal characterized by Dirac nodal lines that disperse exclusively along the out-of-plane direction. With the magnetic field aligned along the nodal line the in-plane Landau level spectra show a nearly $\sqrt{B}$ behavior, the hallmark of a conical-band dispersion with a small spin-orbit coupling gap. The optical conductivity exhibits an unusual temperature-independent isosbestic line, ending at a Van Hove singularity. First-principles calculations unambiguously assign the isosbestic line to transitions across Dirac nodal states. Our work suggests a universal topology of the electronic structure of Dirac nodal lines.