The hallmark of a topologically insulating state of matter in two dimensions protected by time-reversal symmetry is the existence of chiral edge modes propagating along the perimeter of the sample. Among the first systems predicted to be a two-dimensional topological insulator are bilayers of bismuth. Here we report scanning tunnelling microscopy experiments on bulk Bi crystals that show that a subset of the predicted Bi-bilayers’ edge states are decoupled from the states of the substrate and provide direct spectroscopic evidence of their one-dimensional nature. Moreover, by visualizing the quantum interference of edge-mode quasi-particles in confined geometries, we demonstrate their remarkable coherent propagation along the edge with scattering properties consistent with strong suppression of backscattering as predicted for the propagating topological edge states.
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The work at Princeton and the Princeton Nanoscale Microscopy Laboratory was supported by the ARO MURI program W911NF-12-1-0461, DARPA-SPWAR Meso program N6601-11-1-4110, NSF-DMR1104612, NSF CAREER DMR-095242, ONR- N00014-11-1-0635, and NSF-MRSEC NSF-DMR0819860 programs. S.N-P. acknowledges support from the European Community through a Marie Curie fellowship (IOF 302937). The authors would like to thank F. Freimuth for providing the results of ab initio calculations and J. Seo and X. Dai for insightful discussions.
The authors declare no competing financial interests.
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Drozdov, I., Alexandradinata, A., Jeon, S. et al. One-dimensional topological edge states of bismuth bilayers. Nature Phys 10, 664–669 (2014). https://doi.org/10.1038/nphys3048
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