  Magnetic rare-earth / non-magnetic metal superlattices are well-known to
display chiral spin helices in the rare-earth layers that propagate coherently
across the non-magnetic layers. However, the underlying mechanism that
preserves the magnetic phase and chirality coherence across the non-magnetic
layers has remained elusive. In this Letter, we use resonant and
element-specific x-ray scattering to evidence directly the formation of two
fundamentally different long-range modulations in a Holmium/Yttrium (Ho/Y)
multilayer: the known Ho chiral spin helix with periodicity 25 {\AA}, and a
newly observed charge density wave with periodicity 16 {\AA} that propagates
through both the Ho and non-magnetic Y layer. With x-ray circular magnetic
dichroism measurements ruling out the existence of a magnetic proximity effect
induced moment in the non-magnetic Y layers, we propose that the charge density
wave is also chiral, thus providing the means for the transmittance of magnetic
chirality coherence between Ho layers.
