On the effective Dirac dynamics of ultracold atoms in bichromatic   optical lattices
  We study the dynamics of ultracold atoms in tailored bichromatic optical lattices. By tuning the lattice parameters, one can readily engineer the band structure and realize a Dirac point, i.e. a true crossing of two Bloch bands. The dynamics in the vicinity of such a crossing is described by the one-dimensional Dirac equation, which is rigorously shown beyond the tight-binding approximation. Within this framework we analyze the effects of an external potential and demonstrate numerically that it is possible to demonstrate Klein tunneling with current experimental setups. 
D. Witthaut, T. Salger, S. Kling, C. Grossert, and M. Weitz
quant-ph cond-mat.quant-gas