  Recent studies show that periodic potentials can generate superlattice Dirac
points at energies in graphene (is the Fermi velocity of graphene and G is the
reciprocal superlattice vector). Here, we perform scanning tunneling microscopy
and spectroscopy studies of a corrugated graphene monolayer on Rh foil. We show
that the quasi-periodic ripples of nanometer wavelength in the corrugated
graphene give rise to weak one-dimensional (1D) electronic potentials and
thereby lead to the emergence of the superlattice Dirac points. The position of
the superlattice Dirac point is space-dependent and shows a wide distribution
of values. We demonstrated that the space-dependent superlattice Dirac points
is closely related to the space-dependent Fermi velocity, which may arise from
the effect of the local strain and the strong electron-electron interaction in
the corrugated graphene.
