Collective modes of two-dimensional classical Coulomb fluids

TL;DR

This study uses molecular dynamics simulations to analyze collective modes in two-dimensional Coulomb fluids, comparing results with theoretical models and exploring how coupling strength affects wave propagation.

Contribution

It provides a detailed comparison between simulation results and the quasi-crystalline approximation for collective modes in 2D Coulomb fluids, highlighting the conditions for agreement.

Findings

Good agreement for longitudinal modes at moderate coupling

Agreement for transverse modes only at very strong coupling

Derived the cutoff wave-number dependence on coupling strength

Abstract

Molecular dynamics simulations have been performed to investigate in detail collective modes spectra of two-dimensional Coulomb fluids in a wide range of coupling. The obtained dispersion relations are compared with theoretical approaches based on quasi-crystalline approximation (QCA), also known as the quasi-localized charge approximation (QLCA) in the plasma-related context. An overall satisfactory agreement between theory and simulations is documented for the longitudinal mode at moderate coupling and in the long-wavelength domain at strong coupling. For the transverse mode, satisfactory agreement in the long-wavelength domain is only reached at very strong coupling, when the cutoff wave-number below which shear waves cannot propagate becomes small. The dependence of the cutoff wave-number for shear waves on the coupling parameter is obtained.