Double transfer through Dirac points in a tunable honeycomb optical latticeThomas Uehlinger, Daniel Greif, Gregor Jotzu, Leticia Tarruell, Tilman Esslinger, Lei Wang and Matthias TroyerEur. Phys. J. Special Topics, 217 (2013) 121-133DOI: https://doi.org/10.1140/epjst/e2013-01761-y