Spatially resolved electronic structure of twisted graphene

Qirong Yao*, Rik Van Bremen, Guus J. Slotman, Lijie Zhang, Sebastiaan Haartsen, Kai Sotthewes, Pantelis Bampoulis, Paul L. De Boeij, Arie Van Houselt, Shengjun Yuan, Harold J.W. Zandvliet

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

We have used scanning tunneling microscopy and spectroscopy to resolve the spatial variation of the density of states of twisted graphene layers on top of a highly oriented pyrolytic graphite substrate. Owing to the twist a moiré pattern develops with a periodicity that is substantially larger than the periodicity of a single layer graphene. The twisted graphene layer has electronic properties that are distinctly different from that of a single layer graphene due to the nonzero interlayer coupling. For small twist angles (∼1-3.5) the integrated differential conductivity spectrum exhibits two well-defined Van Hove singularities. Spatial maps of the differential conductivity that are recorded at energies near the Fermi level exhibit a honeycomb structure that is comprised of two inequivalent hexagonal sublattices. For energies |E-EF|>0.3eV the hexagonal structure in the differential conductivity maps vanishes. We have performed tight-binding calculations of the twisted graphene system using the propagation method, in which a third graphene layer is added to mimic the substrate. This third layer lowers the symmetry and explains the development of the two hexagonal sublattices in the moiré pattern. Our experimental results are in excellent agreement with the tight-binding calculations.

Original languageEnglish
Article number245116
JournalPhysical review B: Covering condensed matter and materials physics
Volume95
Issue number24
DOIs
Publication statusPublished - 15 Jun 2017

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