The search for proximity-induced superconductivity in topological materials has generated widespread interest in the condensed matter physics community. The superconducting states inheriting nontrivial topology at interfaces are expected to exhibit exotic phenomena such as topological superconductivity and Majorana zero modes, which hold promise for applications in quantum computation. However, a practical realization of such hybrid structures based on topological semimetals and superconductors has hitherto been limited. Here, we report the strong proximity-induced superconductivity in type-II Weyl semimetal WTe₂, in a van der Waals hybrid structure obtained by mechanically transferring NbSe₂ onto various thicknesses of WTe₂. When the WTe₂ thickness (t_WTe2) reaches 21 nm, the superconducting transition occurs around the critical temperature (T_c) of NbSe₂ with a gap amplitude (Δ_p) of 0.38 meV and an unexpected ultralong proximity length (l_p) up to 7 μm. With the thicker 42 nm WTe₂ layer, however, the proximity effect yields T_c ≈ 1.2 K, Δ_p = 0.07 meV, and a short l_p of less than 1 μm. Our theoretical calculations, based on the Bogoliubov–de Gennes equations in the clean limit, predict that the induced superconducting gap is a sizable fraction of the NbSe₂ superconducting one when t_WTe2 is less than 30 nm and then decreases quickly as t_WTe2 increases. This agrees qualitatively well with the experiments. Such observations form a basis in the search for superconducting phases in topological semimetals.

中文翻译：

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通过邻近效应诱导WTe _2中的强超导性

在拓扑材料中寻找邻近感应的超导性已经引起了凝聚态物理学界的广泛兴趣。预计在界面处继承非平凡拓扑的超导状态将表现出奇异现象，例如拓扑超导性和Majorana零模式，这有望在量子计算中得到应用。但是，迄今为止，基于拓扑半金属和超导体的这种混合结构的实际实现受到限制。在这里，我们报道了通过机械地将NbSe ₂机械转移到各种厚度的WTe ₂上而获得的范德华混合结构中的II型Weyl半金属WTe _2中的强邻近感应超导性。当WTe ₂厚度（t _{WTe 2}）达到21 nm时，在NbSe ₂的临界温度（T _c）附近发生超导转变，其间隙幅度（_Δp）为0.38 meV，意外的超长接近长度（l _p）高达7μm 。与较厚的42nm的WTE ₂层，但是，邻近效应产生Ť _Ç ≈1.2 K，Δ _p = 0.07兆电子伏，和一个短的升_p小于1微米。我们基于纯净极限中的Bogoliubov-de Gennes方程的理论计算预测，感应超导间隙是NbSe的相当大的一部分₂当t _{WTe 2}小于30 nm时超导，然后随着t _{WTe 2}增加而迅速减小。这在质量上与实验吻合。这些观察结果为寻找拓扑半金属中的超导相奠定了基础。