  In this letter, we show that asymmetric transmission of circularly polarized
waves through a nanostructured planar chiral graphene film can be observed in
terahertz range. The asymmetric transmission effect of monatomic layer graphene
closely resembles that of metallic planar chiral nanostructures which has
previously been demonstrated. And the relative enantiomeric difference in the
total transmission varies with the change of graphene's Fermi level. The
plasmonic excitation in the graphene nanostructure is the enantiometically
sensitive which is asymmetric for opposite propagating directions. This
phenomenon will deepen our understanding of light-matter interactions in planar
chiral structures and may find applications in polarization-sensitive devices,
sensors, detectors and other areas.
