Bragg Scattering from a Random Potential

A potential for propagation of a wave in two dimensions is constructed from a random superposition of plane waves around all propagation angles. Surprisingly, despite the lack of periodic structure, sharp Bragg diffraction of the wave is observed, analogous to a powder diffraction pattern. The scattering is partially resonant, so Fermi???s golden rule does not apply. This phenomenon would be experimentally observable by sending an atomic beam into a chaotic cavity populated by a single mode laser.

Automated summary

A potential for propagation of a wave in two dimensions is created by randomly superposing plane waves, resulting in a sharp Bragg diffraction pattern similar to powder diffraction. Contrary to expectations, the lack of periodic structure does not prevent the observation of this phenomenon. The scattering in a chaotic cavity is partially resonant and does not follow Fermi's golden rule.