title: Wave dispersion relations in two-dimensional Yukawa systems.
abstract: Collective modes in a two-dimensional Yukawa system are investigated by molecular dynamics simulation in a wide range of coupling parameter Gamma and screening strength kappa. The dispersion relations and sound speeds of the transverse and longitudinal waves obtained for hexagonal lattice are in agreement with the theoretical results. The negative dispersion of the longitudinal wave is demonstrated. Frequency gaps are found on the dispersion curves of the transverse wave due to scattering of the waves on lattice defects for proper values of Gamma. The common frequency of transverse and longitudinal waves drops dramatically with the increasing screening strength kappa.
authors.affiliation: Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China. yuliu@aphy.iphy.ac.cn
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Liu
authors.forename: Bin
authors.initials: B
authors.lastname: Liu
authors.forename: Yanping
authors.initials: Y
authors.lastname: Chen
authors.forename: Si-Ze
authors.initials: SZ
authors.lastname: Yang
authors.forename: Long
authors.initials: L
authors.lastname: Wang
authors.forename: Xiaogang
authors.initials: X
authors.lastname: Wang