Dirac Line Nodes in Inversion Symmetric Crystals

Understand

We propose and characterize a new $\mathbb{Z}_2$ class of topological semimetals with a vanishing spin--orbit interaction.

• The proposed topological semimetals are characterized by the presence of bulk one-dimensional (1D) Dirac Line Nodes (DLNs) and two-dimensional (2D) nearly-flat surface states, protected by inversion and time--reversal symmetries.
• We develop the $\mathbb{Z}_2$ invariants dictating the presence of DLNs based on parity eigenvalues at the parity--invariant points in reciprocal space.
• Moreover, using first-principles calculations, we predict DLNs to occur in Cu$_3$N near the Fermi energy by doping non-magnetic transition metal atoms, such as Zn and Pd, with the 2D surface states emerging in the projected interior of the DLNs.