  A so-called artificial graphene is an artificial material whose low-energy
carriers are described by the massless Dirac equation. Applying a periodic
potential with triangular symmetry to a two-dimensional electron gas is one way
to make such a material. According to recent experimental results, it is now
possible to realize an artificial graphene in the lab and to even apply an
additional lateral, one-dimensional periodic potential to it. We name the
latter system an artificial graphene superlattice in order to distinguish it
from a genuine graphene superlattice made from graphene. In this study, we
investigate the electronic structure of artificial graphene superlattices,
which exhibit the emergence of energy band gaps, merging and splitting of the
Dirac points, etc. Then, from a similar investigation on genuine graphene
superlattices, we show that many of these features originate from the coupling
between Dirac fermions residing in two different valleys, the intervalley
coupling. Furthermore, contrary to previous studies, we find that the effects
of intervalley coupling on the electronic structure cannot be ignored no matter
how long the spatial period of the superlattice is.
