Valley-polarized beam propagation in metallic photonic graphene

International audience; We investigate the electromagnetic wave propagation in a triangular metallic photonic graphene structure and show that, associated to trigonally warped Dirac cones, the transport properties resulting from an incident beam at the armchair edge display drastically different behaviors as compared to the results obtained for other analogous systems. Namely, associated to the lower Dirac cone, the incident beam is collimated to one center beam; while, associated to the upper cone, it is split into two beams with a 2π/3 angle. The other expected beams are all strongly inhibited. This can be related to the metallic nature of the structure, where a propagating electromagnetic wave should follow the structure locals patterns that govern its field distribution, whose symmetry properties determine its excitation by an incident wave. This study highlights the singularity of a metallic photonic graphene in its interaction with the electromagnetic waves, and may find applications in valley photonics for high efficiency collimating and large angle beam splitting system designs.