The phonon wake behind a charge moving relative to a 2D plasma crystal

In a recent experiment a wake was created in a 2D lattice of charged dust grains by a charge moving parallel to the lattice plane. Multiple "Mach cones" were observed in the wake. This paper describes a linear theory of the phonon wake caused by a charge moving relative to a crystalline lattice. The theory predicts multiple structures in the wake that match those observed in the experiments. These structures ale caused by constructive interference of compressional phonons excited by the moving charge, combined with the strongly dispersive nature of these phonons. The theoretical wake is matched to an experimental wake in order to determine the plasma Debye length and the charge on the dust grains.