Sánchez-Barriga, J.; Varykhalov, A.; Marchenko, D.; Scholz, M.R.; Rader, O.: Minigap isotropy and broken chirality in graphene with periodic corrugation enhanced by cluster superlattices. Physical Review B 85 (2012), p. 201413(R)/1-5
10.1103/PhysRevB.85.201413

Abstract:
The chirality of charge carriers in graphene determines its peculiar scattering properties and in particular the avoided backscattering, predicted to be observable in periodically corrugated graphene as the closing of the so-calledminigaps. These are small gaps appearing in the graphene π band at the crossings with umklapp-induced replica bands of the Dirac cone. By angle-resolved photoemission of corrugated graphene on Ir(111), we observe that the minigaps are instead isotropic and close nowhere in k space, unexpected for chiral charge carriers. Artificially enhancing the periodic superpotential by deposition of Au and Ir clusters confirms the minigap isotropy, indicating that the origin of this behavior is directly connected to the broken chirality in the system.