Dimensionality crossover in superconducting wire networks

We have fabricated wire networks in the form of triangular arrays of third-order Sierpinski gaskets and percolation arrays on square lattices. For the gaskets the superconducting phase boundary, ${\mathrm{T}}_{\mathrm{c}}$(H), exhibits a clear crossover between the homogeneous and inhomogeneous (fractal) regimes. This is formally equivalent to the phonon-fracton crossover. Surprisingly, the random, square-lattice percolation networks, which are expected to exhibit a similar crossover, seem to behave in a manner characteristic of two-dimensional systems, independent of length scale.