  We report unexpected classical and quantum dynamics of a wave propagating in
a periodic potential in high Brilloiun zones. Branched flow appears at
wavelengths shorter than the typical length scale of the ordered periodic
structure and for energies above the potential barrier. The strongest branches
remain stable indefinitely and may create linear dynamical channels, wherein
waves are not confined directly by potential walls as electrons in ordinary
wires, but rather indirectly and more subtly by dynamical stability. We term
these superwires, since they are associated with a superlattice.
