Title
Intact dirac cones at broken sublattice symmetry : photoemission study of graphene on Ni and Co Intact dirac cones at broken sublattice symmetry : photoemission study of graphene on Ni and Co
Author
Faculty/Department
Faculty of Sciences. Physics
Publication type
article
Publication
College Park, Md :American Physical Society ,
Subject
Physics
Source (journal)
Physical review X / American Physical Society. - College Park, Md, 2011, currens
Volume/pages
2(2012) :4 , p. 1-10
ISSN
2160-3308
Article Reference
041017
Carrier
E-only publicatie
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
The appearance of massless Dirac fermions in graphene requires two equivalent carbon sublattices of trigonal shape. While the generation of an effective mass and a band gap at the Dirac point remains an unresolved problem for freestanding extended graphene, it is well established by breaking translational symmetry by confinement and by breaking sublattice symmetry by interaction with a substrate. One of the strongest sublattice-symmetry-breaking interactions with predicted and measured band gaps ranging from 400 meV to more than 3 eV has been attributed to the interfaces of graphene with Ni and Co, which are also promising spin-filter interfaces. Here, we apply angle-resolved photoemission to epitaxial graphene on Ni (111) and Co(0001) to show the presence of intact Dirac cones 2.8 eV below the Fermi level. Our results challenge the common belief that the breaking of sublattice symmetry by a substrate and the opening of the band gap at the Dirac energy are in a straightforward relation. A simple effective model of a biased bilayer structure composed of graphene and a sublattice-symmetry-broken layer, corroborated by density-functional-theory calculations, demonstrates the general validity of our conclusions.
Full text (open access)
https://repository.uantwerpen.be/docman/irua/faac4a/3653.pdf
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