Fermi-arcs and non-local collective modes in thin-film Weyl systems*

Fermi-arcs in Weyl semimetals carry signatures of their topological origin. In a thin-film geometry, in the presence of Coulomb interactions, particle-hole excitations can take place either on the same surface, or between the two surfaces, giving rise to the possibility of unique non-local collective modes. We study, in particular, plasmonic modes that are non-locally bound in a thin-film Weyl semimetal carrying the signature of bulk and surface mixing and analyze the possibility of their application.