  Unusual dispersion properties are observed in a phononic crystal of nylon
rods in water when the lattice constant is adjusted so that Bragg and
hybridization gaps overlap in frequency. On the basis of experimental and
numerical analyses of time-dependent transmission and spatial field maps, the
presence of two coexisting propagation modes of similar amplitude is
demonstrated near the resonance frequency. This phenomenon is attributed to the
coupling of the rod resonances arranged in a triangular lattice, with phase
shifts driven by the Bragg condition.
