A single atomic slice of {\alpha}-tin-stanene-has been predicted to host quantum spin Hall effect at room temperature, offering an ideal platform to study low-dimensional and topological physics. While recent research has intensively 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 unexpectedly discover superconductivity in few-layer stanene down to a bilayer grown on PbTe, while bulk {\alpha}-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. Interestingly, the theory also indicates the existence of a topologically nontrivial band. Our experimental findings open up novel strategies for constructing two-dimensional topological superconductors.
@article{arxiv.1712.03695,
title = {Superconductivity in Few-Layer Stanene},
author = {Menghan Liao and Yunyi Zang and Zhaoyong Guan and Haiwei Li and Yan Gong and Kejing Zhu and Xiao-Peng Hu and Ding Zhang and Yong Xu and Ya-Yu Wang and Ke He and Xu-Cun Ma and Shou-Cheng Zhang and Qi-Kun Xue},
journal= {arXiv preprint arXiv:1712.03695},
year = {2018}
}