Inducing Strong Superconductivity in WTe2 by a Proximity Effect

The search for proximity-induced conductivity in topological materials has generated wide-NbSe2, spread 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 OAT-superconductors has hitherto been limited. Here, we report 7 8 0 the strong proximity -induced superconductivity in type -II Weyl semimetal WTe, in a van der Waals hybrid structure obtained by mechanically transferring NbSe2 onto various thicknesses of WTe2. When the WTe2 thickness (twre) reaches 21 mu m, the superconducting transition occurs around the critical temperature (V of NbSe2 with a gap amplitude (op) of 0.38 meV and an unexpected ultralong proximity length (in) up to 7 mu m. With the thicker 42 mu m WTe2 layer, however, the proximity effect yields T-c approximate to 1.2 K, Op = 0.07 meV, and a short 1p of less than 1 mu m. 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 twre, 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.