Collective modes in two-dimensional binary Yukawa systems

Kalman, G. J. and Hartmann, Péter and Donkó, Zoltán and Golden, K. I. and Kyrkos, S. (2013) Collective modes in two-dimensional binary Yukawa systems. PHYSICAL REVIEW E - STATISTICAL, NONLINEAR AND SOFT MATTER PHYSICS (2001-2015), 87 (4). ISSN 1539-3755

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Abstract

We analyze via theoretical approaches and molecular dynamics simulations the collective mode structure of strongly coupled two-dimensional binary Yukawa systems, for selected density, mass and charge ratios, both in the liquid and crystalline solid phases. Theoretically, the liquid phase is described through the Quasi-Localized Charge Approximation (QLCA) approach, while in the crys- talline phase we study the centered honeycomb and the staggered rectangular crystal structures through the standard harmonic phonon approximation. We identify “longitudinal” and “trans- verse” acoustic and optic modes and find that the longitudinal acoustic mode evolves from its weakly coupled counterpart in a discontinuous non-perturbative fashion. The low frequency acous- tic excitations are governed by the oscillation frequency of the average atom, while the high fre- quency optic excitation frequencies are related to the Einstein frequencies of the systems.

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