Long-range proximity effect in aluminum thin films with spatially modulatedTc

We report resistive measurements on a thin-film analog of a modulated-transition-temperature superlattice. The aluminum film was reactive-ion etched in strips perpendicular to the current path, decreasing ${\mathit{T}}_{\mathit{c}}$ of the etched sections by ≊2%, thus spatially modulating the transition temperature. At current densities ≤600 A/${\mathrm{cm}}^2$, the resulting structures exhibit a single homogeneous transition for etched lengths up to 50 μm, substantially longer than expected from the order-parameter decay length of 0.81 μm for the proximity effect in the dirty limit.