Graphene/h-BN has emerged as a model van der Waals heterostructure, and theband structure engineering by the superlattice potential has led to variousnovel quantum phenomena including the self-similar Hofstadter butterfly states.Although newly generated second generation Dirac cones (SDCs) are believed tobe crucial for understanding such intriguing phenomena, so far fundamentalknowledge of SDCs in such heterostructure, e.g. locations and dispersion ofSDCs, the effect of inversion symmetry breaking on the gap opening, stillremains highly debated due to the lack of direct experimental results. Here wereport first direct experimental results on the dispersion of SDCs in 0$^\circ$aligned graphene/h-BN heterostructure using angle-resolved photoemissionspectroscopy. Our data reveal unambiguously SDCs at the corners of thesuperlattice Brillouin zone, and at only one of the two superlattice valleys.Moreover, gaps of $\approx$ 100 meV and $\approx$ 160 meV are observed at theSDCs and the original graphene Dirac cone respectively. Our work highlights theimportant role of a strong inversion symmetry breaking perturbation potentialin the physics of graphene/h-BN, and fills critical knowledge gaps in the bandstructure engineering of Dirac fermions by a superlattice potential.
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