Dirac nodal-line semimetal zinc polynitride at high pressure

Topological semimetals exhibit novel quantum states and electronic structures with interesting Fermi surfaces. In contrast to Weyl and Dirac nodal points, nodal lines can have multiple topological configurations in momentum space that lead to new properties, such as long-range Coulomb interaction and flat Landau levels. Herein, we report the discovery of a Dirac nodal-line semimetal polynitride ${\mathrm{ZnN}}_{4}$, synthesized from the elements under high pressure via laser-heated diamond anvil cell technique. The crystal structure of ${\mathrm{ZnN}}_{4}$ has an $Ibam$ space group, and features infinite one-dimensional nitrogen chains in the pressure range of 14--130 GPa. The Dirac cone is observed midway between $S$ and $X$ points in the Brillouin zone and the Dirac nodal-line is found near the $T$ point. The measured electrical resistance of the ${\mathrm{ZnN}}_{4}$ sample shows an anomalous increase with pressure, which is attributed to the localization of valence electrons. The case of ${\mathrm{ZnN}}_{4}$ provides a unique example of Dirac nodal-line semimetal in nitrides.