Graphene on incommensurate substrates: Trigonal warping and emerging Dirac cone replicas with halved group velocity

Physical Review B (Impact Factor: 3.74). 11/2011; DOI: 10.1103/PhysRevB.86.081405
Source: arXiv


The adhesion of graphene on slightly lattice-mismatched surfaces, for
instance of hexagonal boron nitride (hBN) or Ir(111), gives rise to a complex
landscape of sublattice symmetry-breaking potentials for the Dirac fermions.
Whereas a gap at the Dirac point opens for perfectly lattice-matched graphene
on hBN, we show that the small lattice incommensurability prevents the opening
of this gap and rather leads to a renormalized Dirac dispersion with a trigonal
warping. This warping breaks the effective time reversal symmetry in a single
valley. On top of this a new set of massless Dirac fermions is generated, which
are characterized by a group velocity that is half the one of pristine

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Available from: Jeroen van den Brink
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    • "Graphene-hBN composite system has also been intensively studied as another example of incommensurate multilayer system, where the two layers share the same hexagonal lattice structure but with slightly-different lattice constants, leading to the long-period modulation even at zero rotation angle [15] [16] [17] [18] [19] [20] [21]. The electronic structure in graphene-hBN system was theoretically studied [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35], and the recent transport measurements revealed remarkable effects such as the formation of mini-Dirac bands and the fractal subband structure in magnetic fields [36] [18] [19] [20]. The previous theoretical works mainly targeted the honeycomb lattice to model twisted bilayer graphene and graphene-hBN system, and also particularly focus on the long-period moiré modulation which arises when the crystal structures of two layers are slightly different. "
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