Effect of strong wakes on waves in two-dimensional plasma crystals

TL;DR

This paper investigates how particle-wake interactions influence wave modes in two-dimensional plasma crystals, revealing mode coupling, elliptical polarization, and shifts in hybrid modes with potential experimental signatures.

Contribution

It introduces a detailed analysis of wake-induced mode coupling and polarization changes in plasma crystal waves, highlighting effects not previously characterized.

Findings

Wake-induced mode attraction and elliptical polarization

Rotation of polarization ellipses by 45 degrees during hybridization

Shift of hybrid mode towards smaller wave numbers at strong coupling

Abstract

We study effects of the particle-wake interactions on the dispersion and polarization of dust lattice wave modes in two-dimensional plasma crystals. Most notably, the wake-induced coupling between the modes causes the branches to "attract" each other, and their polarizations become elliptical. Upon the mode hybridization the major axes of the ellipses (remaining mutually orthogonal) rotate by $45^\circ$. To demonstrate importance of the obtained results for experiments, we plot spectral densities of the longitudinal and transverse waves revealing distinct fingerprints of the mixed polarization. Furthermore, we show that at strong coupling the hybrid mode is significantly shifted towards smaller wave numbers, away from the border of the first Brillouin zone (where the hybrid mode is localized for a weak coupling).