Research Article

Inducing metallicity in graphene nanoribbons via zero-mode superlattices

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Science  25 Sep 2020:
Vol. 369, Issue 6511, pp. 1597-1603
DOI: 10.1126/science.aay3588

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Making metallic ribbons

In its usual two-dimensional form, graphene does not have an energy gap in its electronic structure. However, one-dimensional ribbons made of the material are semiconducting and making them metallic is tricky. Rizzo et al. developed a strategy for synthesizing metallic graphene nanoribbons and demonstrated their metallicity using scanning tunneling spectroscopy. These metallic graphene nanoribbons may be useful for exploring exotic quantum phases in a single dimension.

Science, this issue p. 1597

Abstract

The design and fabrication of robust metallic states in graphene nanoribbons (GNRs) are challenging because lateral quantum confinement and many-electron interactions induce electronic band gaps when graphene is patterned at nanometer length scales. Recent developments in bottom-up synthesis have enabled the design and characterization of atomically precise GNRs, but strategies for realizing GNR metallicity have been elusive. Here we demonstrate a general technique for inducing metallicity in GNRs by inserting a symmetric superlattice of zero-energy modes into otherwise semiconducting GNRs. We verify the resulting metallicity using scanning tunneling spectroscopy as well as first-principles density-functional theory and tight-binding calculations. Our results reveal that the metallic bandwidth in GNRs can be tuned over a wide range by controlling the overlap of zero-mode wave functions through intentional sublattice symmetry breaking.

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