Topological valley currents via ballistic edge modes in graphene superlattices near the primary Dirac point
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Li, Y., Amado, M., Hyart, T., Mazur, G., & Robinson, J. (2020). Topological valley currents via ballistic edge modes in graphene superlattices near the primary Dirac point. Communications Physics, 3 (1)https://doi.org/10.1038/s42005-020-00495-y
Graphene on hexagonal boron nitride (hBN) can exhibit a topological phase via mutual crystallographic alignment. Recent measurements of nonlocal resistance (Rnl) near the secondary Dirac point (SDP) in ballistic graphene/hBN superlattices have been interpreted as arising due to the quantum valley Hall state. We report hBN/graphene/hBN superlattices in which Rnl at SDP is negligible, but below 60 K approaches the value of h/2e2 in zero magnetic field at the primary Dirac point with a characteristic decay length of 2 μm. Furthermore, nonlocal transport transmission probabilities based on the Landauer-Büttiker formalism show evidence for spin-degenerate ballistic valley-helical edge modes, which are key for the development of valleytronics.
The research was funded by the Royal Society and the EPSRC through an EPSRC-JSPS International Network Grant (EP/P026311/1). Y.L. was supported through China Scholarship Council (CSC) Cambridge International Scholarship and Cambridge Trust. M.A. was supported from the MSCA-IFEF-ST Marie Curie (Grant 656485-Spin3), the Agencia Estatal de Investigación of Spain (Grant MAT2016-75955), and the Junta de Castilla y León (Grant SA256P18). T.H. and G.P.M were supported by the Foundation for Polish Science through the IRA Programme co-financed by EU within SG OP. G.P.M. was supported by the National Science Center (Poland) through ETIUDA fellowship (Grant No. UMO-2017/24/T/ST3/00501).
European Commission (656485)
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External DOI: https://doi.org/10.1038/s42005-020-00495-y
This record's URL: https://www.repository.cam.ac.uk/handle/1810/312755
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