Synchronization of particle motion in compressed two-dimensional plasma crystals (original) (raw)
Related papers
Synchronization of particle motion induced by mode coupling in a two-dimensional plasma crystal
Physical Review E, 2014
The kinematics of dust particles during the early stage of mode-coupling induced melting in a two-dimensional plasma crystal is explored. The formation of the hybrid mode induces the partial synchronisation of the particle vibrations at the hybrid frequency. A rhythmic pattern of alternating in-phase and anti-phase oscillating chains of particles is observed. The spatial orientation of the synchronisation pattern correlates well with the directions of the maximal increment of the shear-free hybrid mode.
Direct Observation of Mode-Coupling Instability in Two-Dimensional Plasma Crystals
Physical Review Letters, 2010
Dedicated experiments on melting of 2D plasma crystals were carried out. The melting was always accompanied by spontaneous growth of the particle kinetic energy, suggesting a universal plasma-driven mechanism underlying the process. By measuring three principal dust-lattice (DL) wave modes simultaneously, it is unambiguously demonstrated that the melting occurs due to the resonance coupling between two of the DL modes. The variation of the wave modes with the experimental conditions, including the emergence of the resonant (hybrid) branch, reveals exceptionally good agreement with the theory of mode-coupling instability.
Anisotropic confinement effects in a two-dimensional plasma crystal
Physical review. E, 2016
The spectral asymmetry of the wave-energy distribution of dust particles during mode-coupling-induced melting, observed for the first time in plasma crystals by Couëdel et al. [Phys. Rev. E 89, 053108 (2014)PLEEE81539-375510.1103/PhysRevE.89.053108], is studied theoretically and by molecular-dynamics simulations. It is shown that an anisotropy of the well confining the microparticles selects the directions of preferred particle motion. The observed differences in intensity of waves of opposed directions are explained by a nonvanishing phonon flux. Anisotropic phonon scattering by defects and Umklapp scattering are proposed as possible reasons for the mean phonon flux.
Nonlinear regime of the mode-coupling instability in 2D plasma crystals
EPL (Europhysics Letters), 2014
The transition between linear and nonlinear regimes of the mode-coupling instability (MCI) operating in a monolayer plasma crystal is studied. The mode coupling is triggered at the centre of the crystal and a melting front is formed, which travels through the crystal. At the nonlinear stage, the mode coupling results in synchronisation of the particle motion and the kinetic temperature of the particles grows exponentially. After melting of the crystalline structure, the mean kinetic energy of the particles continued to grow further, preventing recrystallisation of the melted phase. The effect could not be reproduced in simulations employing a simple point-like wake model. This shows that at the nonlinear stage of the MCI a heating mechanism is working which was not considered so far.
Dynamics of spinning particle pairs in a single-layer complex plasma crystal
Physical Review E, 2017
Spontaneous formation of spinning pairs of particles, or torsions was studied in a single-layer complex plasma crystal by reducing the discharge power at constant neutral gas pressure. At higher gas pressures, torsions spontaneously formed below a certain power threshold. Further reduction of the discharge power led to the formation of multiple torsions. However, at lower gas pressures the torsion formation was preceded by the mode-coupling instability (MCI). The crystal dynamics were studied with the help of the fluctuation spectra of crystal particles' in-plane velocities. Surprisingly, the spectra of the crystal with torsions and MCI are rather similar and contain "hot spots" at similar locations on the (k, ω) plane, despite very different appearances of the respective particle trajectories. The torsion rotation speed was close (slightly below) to the maximum frequency of the in-plane compressional mode. When multiple torsions formed, their rotation speeds were distributed in a narrow range slightly below the maximum frequency.
Crystallization Dynamics of a Single Layer Complex Plasma
Physical Review Letters, 2010
We report a series of complex (dusty) plasma experiments, aimed at the study of the detailed time evolution of the re-crystallisation process following a rapid quench of a two dimensional dust liquid. The experiments were accompanied by large-scale (million particle) molecular dynamics simulations, assuming Yukawa type inter-particle interaction. Both experiment and simulation show a ∝ t α (power law) dependence of the linear crystallite domain size as measured by the bondorder correlation length, translational correlation length, dislocation (defect) density, and a direct size measurement algorithm. The results show two stages of order formation: on short time-scales individual particle motion dominates; this is a fast process characterized by α = 0.93 ± 0.1. At longer time-scales, small crystallites undergo collective rearrangement, merging into bigger ones, resulting in a smaller exponent α = 0.38 ± 0.06.
Observation of particle pairing in a two-dimensional plasma crystal
Physical Review E, 2014
The observation is presented of naturally occurring pairing of particles and their cooperative drift in a two-dimensional plasma crystal. A single layer of plastic microspheres was suspended in the plasma sheath of a capacitively coupled rf discharge in argon at a low pressure of 1 Pa. The particle dynamics were studied by combining the top-view and side-view imaging of the suspension. Cross analysis of the particle trajectories allowed us to identify naturally occurring metastable pairs of particles. The lifetime of pairs was long enough for their reliable identification.
Effect of confinement on the crystallization of a dusty plasma in narrow channels
JETP Letters, 2008
Three-dimensional quasi-equilibrium configurations of a complex (dusty) plasma in narrow channels are investigated using the molecular dynamics simulations for various confining potentials (confinements). The dynamics of the microparticles is described within the framework of a Langevin thermostat with allowance for the pair interaction between charged particles, which is described by a screened Coulomb potential (Yukawa potential). Two confinements-the parabolic potential and hard elastic wall-are considered. It is shown that the confinement strongly affects the crystallization and the local order of the microparticles in the system under consideration; in particular, the appearance of a new quasicrystalline phase induced by the hard wall confinement is revealed.
Physics Letters A, 2003
A comprehensive study of the Debye-Hückel repulsive and ion wakefield induced attractive potentials around a dust grain is presented, including ion flow. It is found that the modified interaction potential (especially the attractive wakefield force) can cause instability of linear dust oscillations propagating in a dusty plasma crystal composed of dust grains in a horizontal arrangement suspended in the sheath region near a conducting wall (electrode). The dependence of dust lattice modes on the ion flow is studied, revealing instability of dust lattice modes for certain values of the ion flow speed.