Interfaces of nodal-line semimetals: Drum states, transport, and refraction

We study transport through interfaces in topological nodal-line semimetal (NLS), focusing on two geometries: a single interface between two large samples, one NLS and one metal, and an infinite NLS slab in between two metallic regions. We investigate the dependence of the spectra on the boundary conditions, showing how they affect the surface states and the band dispersion. We find a set of drum states, arising from the hybridization of the drumhead states on opposite surfaces at finite slab width, and describe their signatures in the transport properties of a clean sample. Finally, we compute the electronic trajectories in the ballistic regime and show that there is a series of resonant angles that ensure perfect transmission. We also show how the current density profile acquires an inhomogeneous distribution in the radial direction.