When disorder stops scattering waves

Disorder is usually associated with wave scattering: when a wave encounters many randomly positioned obstacles, it is progressively redirected and loses its directionality. Yet some structures remain disordered while displaying specific spatial correlations, known as hyperuniform correlations, that can profoundly alter wave propagation.

Theory had predicted that such correlated disorder could suppress scattering over specific wavelength ranges: without changing either the scatterers or their density, simply rearranging them can make the medium nearly transparent [2].

In a study published in the Proceedings of the National Academy of Sciences (PNAS), researchers from Institut Langevin provide a direct experimental observation of this phenomenon using surface water waves. It is possible to measure the amplitude and phase of the whole wavefield at all times inside media containing hundreds of scatterers arranged either randomly or in a stealthy hyperuniform pattern.

The experiments reveal a sharp transition: at long wavelengths, the wavefront propagates through the hyperuniform medium almost undisturbed, while it is strongly scattered by the random medium. Beyond the theoretically predicted threshold, scattering reappears. The same transition is observed in wave extinction, statistical fluctuations and energy-flow trajectories.

Surface water waves provide a particularly visual and controllable experimental platform for revealing a universal mechanism: using the hidden correlations within disorder to control wave propagation. These principles can therefore be extended across wave physics, from acoustics and optics to wave-based materials.