Abstract

A single atomic slice of α-tin—stanene—has been predicted to host the quantum spin Hall effect at room temperature, offering an ideal platform to study low-dimensional and topological physics. Although recent research has focused on monolayer stanene, the quantum size effect in few-layer stanene could profoundly change material properties, but remains unexplored. By exploring the layer degree of freedom, we discover superconductivity in few-layer stanene down to a bilayer grown on PbTe, while bulk α-tin is not superconductive. Through substrate engineering, we further realize a transition from a single-band to a two-band superconductor with a doubling of the transition temperature. In situ angle-resolved photoemission spectroscopy (ARPES) together with first-principles calculations elucidate the corresponding band structure. The theory also indicates the existence of a topologically non-trivial band. Our experimental findings open up novel strategies for constructing two-dimensional topological superconductors.

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Acknowledgements

We thank Hong Yao and Canli Song for useful discussions. This work is financially supported by the Ministry of Science and Technology of China (2017YFA0304600, 2017YFA0302902), the National Natural Science Foundation of China (grant no. 11604176) and the Beijing Advanced Innovation Center for Future Chip (ICFC). Y.X. acknowledges support from Tsinghua University Initiative Scientific Research Program and the National Thousand-Young-Talents Program. 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.

Author information

Author notes

  1. Menghan Liao and Yunyi Zang contributed equally to this work.

Affiliations

  1. State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, China

    • Menghan Liao
    • , Yunyi Zang
    • , Zhaoyong Guan
    • , Haiwei Li
    • , Yan Gong
    • , Kejing Zhu
    • , Xiao-Peng Hu
    • , Ding Zhang
    • , Yong Xu
    • , Ya-Yu Wang
    • , Ke He
    • , Xu-Cun Ma
    •  & Qi-Kun Xue
  2. Collaborative Innovation Center of Quantum Matter, Beijing, China

    • Xiao-Peng Hu
    • , Ding Zhang
    • , Yong Xu
    • , Ya-Yu Wang
    • , Ke He
    • , Xu-Cun Ma
    •  & Qi-Kun Xue
  3. RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, Japan

    • Yong Xu
  4. Department of Physics, McCullough Building, Stanford University, Stanford, CA, USA

    • Shou-Cheng Zhang

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Contributions

M.L. and Y.Z. contributed equally to this work. D.Z., K.H. and Q.-K.X. conceived the project. Y.Z. grew the samples and carried out ARPES measurements with the assistance of Y.G., M.L. and D.Z. carried out the transport measurements with the assistance of K.Z., M.L., D.Z., H.L., X.-P.H. and Y.-Y.W. made the two-coil mutual inductance measurements. Z.G. and Y.X. carried out first-principles calculations. D.Z. and Y.X. analysed the data and wrote the paper with input from K.H., X.-C.M., S.-C.Z. and Q.-K.X. All authors discussed the results and commented on the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Ding Zhang or Yong Xu or Qi-Kun Xue.

Supplementary information

  1. Extended data

    Extended data Figs. 1–6.

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https://doi.org/10.1038/s41567-017-0031-6

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