Strongly coupled Yukawa trilayer liquid: Structure and dynamics

TL;DR

This paper investigates the structure and collective excitations of strongly coupled trilayer Yukawa liquids using theoretical and simulation methods, revealing new phenomena and insights into their dynamic behavior.

Contribution

It combines the Quasi-Localised Charge Approximation with molecular dynamics simulations to analyze collective modes and uncovers phenomena beyond existing theories.

Findings

QLCA provides accurate dispersion relations

Discovery of a novel structure in current fluctuation spectra

Insights into the gap frequency discrepancy in layered systems

Abstract

The equilibrium structure and the dispersion relations of collective excitations in trilayer Yukawa systems in the strongly coupled liquid regime are examined. The equilibrium correlations reveal a variety of structures in the liquid phase, reminiscent of the corresponding structures in the solid phase. At small layer separation substitutional disorder becomes the governing feature. Theoretical dispersion relations are obtained by applying the Quasi-Localised Charge Approximation (QLCA) formalism, while numerical data are generated by micro-canonical molecular dynamics (MD) simulations. The dispersions and polarizations of the collective excitations obtained through both of these methods are compared and discussed in detail. We find that the QLCA method is, in general, very satisfactory, but that there are phenomena not covered by the QLCA. In particular, by analyzing the dynamical longitudinal and transverse current fluctuation spectra we discover the existence of a novel structure, not related to the collective mode spectra. This also provides a new insight into the long-standing problem of the gap frequency discrepancy, observed in strongly coupled layered systems in earlier studies.