Electronic and mechanical realizations of one-way coupling in one and two dimensions.

One-way or unidirectional coupling is a striking example of how topological considerations--the parity of an array of multistable elements combined with periodic boundary conditions--can qualitatively influence dynamics. Here we introduce a simple electronic model of one-way coupling in one and two dimensions and experimentally compare it to an improved mechanical model and an ideal mathematical model. In two dimensions, computation and experiment reveal richer one-way coupling phenomenology: in media where two-way coupling would dissipate all excitations, one-way coupling enables solitonlike waves to propagate in different directions with different speeds.