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.

据预测，一个单原子的α-锡（锡）原子切片将在室温下产生量子自旋霍尔效应，为研究低维和拓扑物理提供了理想的平台。尽管最近的研究集中在单层锡上，但几层锡中的量子尺寸效应可能会深刻改变材料的性能，但仍未得到探索。通过探索层的自由度，我们发现了几层锡中的超导性，直到在PbTe上生长的双层为止，而本体α-锡不是超导性的。通过基板工程，我们进一步实现了从单波段到两波段超导体的转变，并且转变温度加倍。原位角分辨光发射光谱（ARPES）与第一原理计算一起阐明了相应的能带结构。该理论还表明存在拓扑非平凡的带。我们的实验结果为构造二维拓扑超导体开辟了新的策略。