  The dispersion relation of ultracold atoms in variably shaped optical
lattices can be tuned to resemble that of a relativistic particle, i.e. be
linear instead of the usual nonrelativistic quadratic dispersion relation of a
free atom. Cold atoms in such a lattice can be used to carry out quantum
simulations of relativistic wave equation predictions. We begin this article by
describing a Raman technique that allows to selectively load atoms into a
desired Bloch band of the lattice near a band crossing. Subsequently, we review
two recent experiments with quasirelativistic rubidium atoms in a bichromatic
lattice, demonstrating the analogs of Klein tunneling and Veselago lensing with
ultracold atoms respectively.
