Model system for vortex motion in coupled two-dimensional type-II superconductors

We report linear electrical transport measurements in ${\mathrm{Mo}}_{77}$ ${\mathrm{Ge}}_{23}$/Ge multilayres and a single layer of ${\mathrm{Mo}}_{77}$ ${\mathrm{Ge}}_{23}$ which is nominally the same as the constituent layers of each multilayer. In the multilayers, we observe a crossover from a regime where the vortex motion displays interlayer coupling to a regime where the vortex segments in each layer move effectively independent. Our observations bear some strong resemblances to those in high-temperature superconductors, and we discuss the possible relevance to our system of some concepts developed to interpret the high-temperature superconductors.