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# One-dimensional topological edge states of bismuth bilayers

## Abstract

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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## Change history

• ### 13 August 2014

In the version of this Article originally published, the name of one of the authors contained a typographical error and should have read B. Andrei Bernevig. This error has now been corrected in all versions of the Article.

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## Acknowledgements

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.

## Author information

Authors

### Contributions

I.K.D., S.J., S.N-P. and A.Y. designed and carried out the STM measurements and their analysis on samples synthesized by H.J. and R.J.C. A.A., I.K.D. and B.B. performed model calculations and related analysis. All authors contributed to the writing of the manuscript.

### Corresponding author

Correspondence to Ali Yazdani.

## Ethics declarations

### Competing interests

The authors declare no competing financial interests.

## Supplementary information

### Supplementary Information

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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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• DOI: https://doi.org/10.1038/nphys3048

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