Topological Surface State in Epitaxial Zigzag Graphene Nanoribbons.

Nguyen, Thi Thuy Nhung; de Vries, Niels; Karakachian, Hrag; Gruschwitz, Markus; Aprojanz, Johannes; Zakharov, Alexei A; Polley, Craig; Balasubramanian, Thiagarajan et al. · Nano Lett · 2021

basic_science · Level V

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Abstract

Protected and spin-polarized transport channels are the hallmark of topological insulators, coming along with an intrinsic strong spin-orbit coupling. Here we identified such corresponding chiral states in epitaxially grown zigzag graphene nanoribbons (zz-GNRs), albeit with an extremely weak spin-orbit interaction. While the bulk of the monolayer zz-GNR is fully suspended across a SiC facet, the lower edge merges into the SiC(0001) substrate and reveals a surface state at the Fermi energy, which is extended along the edge and splits in energy toward the bulk. All of the spectroscopic details are precisely described within a tight binding model incorporating a Haldane term and strain effects. The concomitant breaking of time-reversal symmetry without the application of external magnetic fields is supported by ballistic transport revealing a conduction of <i>G</i> = <i>e</i><sup>2</sup>/<i>h</i>.