  When a linear chain of plasmonic nano-particles is subject to longitudinal
magnetic field, it exhibits optical Faraday rotation. If the magnetized
nano-particles are plasmonic ellipsoids arranged as a spiral chain, the
interplay between the Faraday rotation and the geometrical spiral rotation
(structural chirality) can strongly enhance non-reciprocity. This interplay
forms a waveguide that permits one way propagation only, within four disjoint
frequency bands; two bands for each direction.
