Ballistic tracks in graphene nanoribbons

High quality graphene nanoribbons epitaxially grown on the sidewalls of silicon carbide (SiC) mesa structures stand as key building blocks for graphene-based nanoelectronics. Such ribbons display 1D single-channel ballistic transport at room temperature with exceptionally long mean free paths. Here, using spatially-resolved two-point probe (2PP) measurements, we selectively access and directly image a range of individual transport modes in sidewall ribbons. The signature of the independently contacted channels is a sequence of quantised conductance plateaus for different probe positions. These result from an interplay between edge magnetism and asymmetric terminations at opposite ribbon edges due to the underlying SiC structure morphology. Our findings demonstrate a precise control of transport through multiple, independent, ballistic tracks in graphene-based devices, opening intriguing pathways for quantum information device concepts.
Financial support by the Deutsche Forschungsgemeinschaft (Te386/12-1 and Te 386/13-1 (FlagEra Tailspin project)) is gratefully acknowledged by J.A. and C.T. P.B. and H.J.W.Z. thank the Stichting voor Fundamenteel Onderzoek der Materie (FOM, FV157 14TWDO07) for financial support. We acknowledge N. Vinogradov and Thi Thuy Nhung Nguyen for STM experiments and J. Schommartz for technical support. S.R.P. acknowledges funding from the European Unions Horizon 2020 research and innovation programme under the Marie Skodowska-Curie grant agreement No 665919 and from the Irish Research Council under the laureate awards programme. S.R. acknowledges funding from the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (project no. FIS2015-67767-P MINECO/FEDER, FIS2015-64886-C5-3-P) and the European Union Seventh Framework Programme under grant agreement no. 785219 (Graphene Flagship). ICN2 is funded by the CERCA Programme/Generalitat de Catalunya and supported by the Severo Ochoa programme (MINECO, Grant. No. SEV-2013-0295). Research at DTU is supported by the Danish National Research Foundation, Project No. DNRF103. A.Z. acknowledges the Swedish Research Council (Vetenskapsrådet) for the Tailspin project support.