  We manipulate optical Tamm states in graphene-based photonics to achieve and
steer large magneto-optical effects. Here we report the presence of a giant
Faraday rotation via a single graphene layer of atomic thickness while keeping
a high transmission. The Faraday rotation is enhanced across the interface
between two photonic crystals due to the presence of an interface mode, which
presents a strong electromagnetic field confinement at the location of the
graphene sheet. Our proposed scheme opens a promising avenue to realize high
performance graphene magneto-optical devices that can be extended to other
two-dimensional structures.
