Optical conductivity signatures of open Dirac nodal lines

We investigate the optical conductivity and far-infrared magneto-optical response of BaNiS2, 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 root 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.

Automated summary

The investigation on BaNiS2 reveals the electronic structure with Dirac nodal lines, showing an unusual temperature-independent isosbestic line in optical conductivity that ends at a Van Hove singularity. First-principles calculations demonstrate that this isosbestic line is associated with transitions across Dirac nodal states.