title: Compressional and shear wakes in a two-dimensional dusty plasma crystal.
abstract: Wakes composed of compressional and shear waves were studied experimentally in a two-dimensional screened-Coulomb crystal. Highly charged microspheres suspended in a plasma settled in a horizontal monolayer and arranged in a triangular lattice with a repulsive interparticle potential. Wakes were excited by a moving spot of Ar+ laser light. Depending on the laser spot speed, compressional waves formed a Mach cone and multiple lateral or transverse wakes, similar to ship wakes on the water surface, due to a combination of acoustic and dispersive properties. Shear waves, however, formed only a Mach cone, due to their nearly acoustic, i.e., dispersionless character. The experimental results show agreement with a recently developed theory and with molecular dynamics simulations, which assume a binary Yukawa interparticle potential. A generally useful method is presented for calculating the real part of the dispersion relation of the compressional waves based on the analysis of the spatial structure of a phonon wake. Fitting the resulting dispersion relation provides an independent measure of the interparticle potential, parametrized by the screening parameter kappa and particle charge Q.
authors.affiliation: Department of Physics and Astronomy, The University of Iowa, Iowa City, IA 52242, USA. vladimir.nosenko@uiowa.edu
authors.forename: V
authors.initials: V
authors.lastname: Nosenko
authors.forename: J
authors.initials: J
authors.lastname: Goree
authors.forename: Z W
authors.initials: ZW
authors.lastname: Ma
authors.forename: D H E
authors.initials: DH
authors.lastname: Dubin
authors.forename: A
authors.initials: A
authors.lastname: Piel