  We theoretically investigate the electromagnetic response of a novel class of
multi-layered metamaterials obtained by alternating graphene sheets and
dielectric layers, the whole structure not exhibiting a plane of reflection
symmetry along the stacking direction. We show that the electromagnetic
response of the structure is characterized by a magneto-electric coupling
described by an effective chiral parameter. Exploiting the intrinsic tunability
of the graphene-light coupling, we prove that one can tune both the dielectric
and the chiral electromagnetic response by varying the graphene chemical
potential through external voltage gating.
