  Theory predicts that graphene under uniaxial compressive strain in an
armchair direction should undergo a topological phase transition from a
semimetal into an insulator. Due to the change of the hopping integrals under
compression, both Dirac points shift away from the corners of the Brillouin
zone towards each other. For sufficiently large strain, the Dirac points merge
and an energy gap appears. However, such a topological phase transition has not
yet been observed in normal graphene (due to its large stiffness) neither in
any other electronic system. We show numerically and analytically that such a
merging of the Dirac points can be observed in electronic artificial graphene
created from a two-dimensional electron gas by application of a triangular
lattice of repulsive antidots. Here, the effect of strain is modeled by tuning
the distance between the repulsive potentials along the armchair direction. Our
results show that the merging of the Dirac points should be observable in a
recent experiment with molecular graphene.
