Transmission and conductance across junctions of isotropic and anisotropic three-dimensional semimetals

We compute the transmission coefficients and zero-temperature conductance for chiral quasiparticles propagating through various geometries, which consist of junctions of three-dimensional nodal point semimetals. In the first scenario, we consider a potential step with two Rarita-Schwinger-Weyl or two birefringent semimetals, which are tilted with respect to the other on the two sides of the junction. The second set-up consists of a junction between a doped Dirac semimetal and a ferromagnetic Weyl semimetal, where an intrinsic magnetization present in the latter splits the doubly-degenerate Dirac node into a pair of Weyl nodes. A scalar potential is also applied in the region where the Weyl semimetal phase exists. Finally, we study sandwiches of Weyl/multi-Weyl semimetals, with the middle region being subjected to both scalar and vector potentials. Our results show that a nonzero transmission spectrum exists where the areas, enclosed by the Fermi surface projections (in the plane perpendicular to the propagation axis) of the incidence and transmission regions, overlap. Such features can help engineer unidirectional carrier propagation, topologically protected against impurity backscattering, because of the chiral nature of the charge carriers.