Plasmonic spin induced Imbert-Fedorov shift.

The spin angular momentums of surface plasmon polaritons (SPPs) on chiral material interfaces and the Imbert-Fedorov shifts of linearly polarized light beams are investigated. Compared to a traditional TM-polarized SPP having a transverse spin, the SPP on a chiral material interface also has a longitudinal spin component, resulting from the nature that this new kind of SPP is a hybrid of TE and TM-polarized evanescent waves. When a light beam is incident on a sandwich structure composed of chiral material, prisms, and metal layers, in which the SPP is supported, the reflection and transmission processes can be analogous to the transport of a photon in a waveguide QED system. The SPP with longitudinal spin can be excited by the incident wave and the reflected and transmitted beams carry the spin features of the SPP. Moreover, the beams exhibit large Imbert-Fedorov shifts stemming from the spin-orbit coupling even for a linearly polarized incident beam. The shifts are determined by the longitudinal spin angular momentum and excitation coefficient of the SPP. This present work extends the study of photonic spin-orbit coupling and provides an important platform to investigate the plasmonic spin.