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Epitaxial growth of ultraflat stanene with topological band inversion

Abstract

Two-dimensional (2D) topological materials, including quantum spin/anomalous Hall insulators, have attracted intense research efforts owing to their promise for applications ranging from low-power electronics and high-performance thermoelectrics to fault-tolerant quantum computation. One key challenge is to fabricate topological materials with a large energy gap for room-temperature use. Stanene—the tin counterpart of graphene—is a promising material candidate distinguished by its tunable topological states and sizeable bandgap. Recent experiments have successfully fabricated stanene, but none of them have yet observed topological states. Here we demonstrate the growth of high-quality stanene on Cu(111) by low-temperature molecular beam epitaxy. Importantly, we discovered an unusually ultraflat stanene showing an in-plane s–p band inversion together with a spin–orbit-coupling-induced topological gap (~0.3 eV) at the Γ point, which represents a foremost group-IV ultraflat graphene-like material displaying topological features in experiment. The finding of ultraflat stanene opens opportunities for exploring two-dimensional topological physics and device applications.

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Fig. 1: Atomic and electronic structures of ultraflat stanene on Cu(111).
Fig. 2: Calculated atomic and electronic structures of the ultraflat stanene.
Fig. 3: Edge structure and edge states of the ultraflat stanene flakes.
Fig. 4: Atomically resolved line defect and point defects in the ultraflat stanene.

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The data that support the findings of this study are available from the corresponding authors upon reasonable request.

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Acknowledgements

This work was supported by the National Key R&D Program of China (grants nos 2016YFA0200603, 2017YFA0205004, 2018YFA0305603, 2016YFA0301001, 2018YFA0307100), the ‘Strategic Priority Research Program’ of CAS (XDB01020100), the National Natural Science Foundation of China (grants nos 91321309, 51132007, 21421063, 21473174, 21273210, 51788104), and the Fundamental Research Funds for the Central Universities (WK2060190084, WK2340000065). A.Z. acknowledges a fellowship from the Youth Innovation Promotion Association of CAS (2011322). Y.X. acknowledges support from the Tsinghua University Initiative Scientific Research Program and the National Thousand-Young-Talents Program. The calculations were done on the ‘Explorer 100’ cluster system of Tsinghua University and on the ‘Tianhe-2’ of the National Supercomputer Computer Center in Guangzhou. W.D. acknowledge support from the National Natural Science Foundation of China (grants nos 11674188 and 11334006), and the Beijing Advanced Innovation Center for Future Chip (ICFC). S.-C.Z. is supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Contract No. DE-AC02-76SF00515.

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Contributions

A.Z., Y.X., B.W., W.D., S.-C.Z. and J.G.H. devised the experiments and provided financial and other support for the experiments and calculations. J.D. H.S. and X.Z. performed the MBE growth and STM/STS measurements. B.X., H.C., B.L. and Y.X. performed theoretical calculations. X.M. and J.D. performed the ARPES measurements. A.Z., Y.X., B.W., W.D., S.-C.Z. and J.G.H. analysed the data. A.Z. and Y.X. wrote the paper with input from other co-authors.

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Correspondence to Aidi Zhao, Yong Xu or Bing Wang.

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Supplementary Materials

Supplementary Figures 1–9, Extended Discussion of Computational Results, Supplementary References 1–4

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Deng, J., Xia, B., Ma, X. et al. Epitaxial growth of ultraflat stanene with topological band inversion. Nature Mater 17, 1081–1086 (2018). https://doi.org/10.1038/s41563-018-0203-5

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