Plasmonic valley chiral states in graphene based plasmonic crystals

A new degree of freedom, valley, has recently been introduced into the fields of acoustic and photonic crystals. This provides a promising platform for classical waves to mimic the valley-contrasting properties of condensed matter physics. Here, we study the plasmonic version of valley states in graphene plasmonic crystals of inversion symmetry broken honeycomb lattices. The intrinsic valley vortex feature is unambiguously revealed. The evolution of the valley chiral states involving topological transition is theoretically explored. Furthermore, numerical simulations for the selective excitations of the valley chiral states are carried out in our designed valley plasmonic crystals. Our work has potential applications in the orbital angular momentum-assisted surface plasmon polariton manipulation and the applications of plasmonic valleytronics in nanophotonics and on-chip integration.