Photonic spin-Hall effect in chiral plasmonic assemblies

Directional light splitting based on the photonic spin-Hall effect is a desired feature for the development of spin-dependent optical elements. Here, we report on the routing of surface plasmon polaritons (SPPs) by using chiral gold nanocubes (Au NCs) and silver nanowires (Ag NWs). We experimentally and theoretically observe the photonic spin-Hall effect in Ag NWs under circularly polarized excitation and show that, when Au NCs of opposite chirality are attached to the NWs, linearly polarized illumination can modulate the SPPs formed on the NWs. We achieve directional emission of valley-polarized excitons from hybrid structures made of (chiral Au NC)-(Ag NW) assembled with transition metal dichalcogenide monolayers and observe an enhanced degree of valley polarization. The underlying mechanism of the routing effect is understood through numerical simulations, confirming that the observed chirality-dependent routing effect can have important implications for the development of valleytronic circuits.