Spontaneous pairing and cooperative movements of micro-particles in a two dimensional plasma crystal

Zhdanov, S. K.; Couëdel, Lénaïc; Nosenko, V.; Thomas, Hubertus M.; Morfill, G. E.

doi:10.1063/1.4920967

Cited by 9 publications

(5 citation statements)

References 73 publications

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“…However, care should be taken to clearly separate the generic and plasma-related phenomena which are peculiar to plasma crystals [14]. The latter may be, e.g., mode-coupling instability (MCI) [15][16][17][18], channeling of upstream extra particles [19], or particle pairing [20,21]. Vertical pairs of particles can form in a single-layer plasma crystal spontaneously [20] or after a sudden drop of the neutral gas pressure [21].…”

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confidence: 99%

Dynamics of spinning particle pairs in a single-layer complex plasma crystal

et al. 2017

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Spontaneous formation of spinning pairs of particles, or torsions, is studied in a single-layer complex plasma crystal by reducing the discharge power at constant neutral gas pressure. At higher gas pressures, torsions spontaneously form below a certain power threshold. Further reduction of the discharge power leads to the formation of multiple torsions. However, at lower gas pressures the torsion formation is preceded by mode-coupling instability (MCI). The crystal dynamics are 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 is close (slightly below) to the maximum frequency of the in-plane compressional mode. When multiple torsions form, their rotation speeds are distributed in a narrow range slightly below the maximum frequency.

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confidence: 99%

Dynamics of spinning particle pairs in a single-layer complex plasma crystal

et al. 2017

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“…Many experimental observations of ion wake-induced mode-coupling instability are explained well by the model where the ion wake is described as a pointlike positive charge q > 0 located downstream from the Fig. 5: Particle charge number Z as a function of the interaction range κ for the Einstein frequency ωE = 107 s −1 and a = 0.314 mm assuming the Yukawa interaction potential [24] (solid line) or the critical charge density principle [10] (dashed line). The intersection point corresponds to Z ≈ 13700 and κ ≈ 1.17.…”

Section: How the Flow Of Ions Drives Torsionsmentioning

confidence: 70%

“…An additional constraint can be added in the following way. Spontaneous appearance of coupled particle pairs in the course of an experiment indicates that the crystal is close to the marginally unstable state [10]. Assuming that this is the case, it is easy to roughly estimate both Z and κ; see fig.…”

Section: How the Flow Of Ions Drives Torsionsmentioning

confidence: 96%

“…The typical orbit radius of such "torsion" was about 0.07-0.1 mm, its rotation quasiperiod was about 0.08-0.1 s. Apparently, there was no preference in the torsion spin direction. The entanglement lifetime of a torsion can be distinctly longer than its rotation period: the typical lifetime of the recorded rotating pairs is about 1-4 s. In the high-pressure regime, which effectively suppresses perturbations as compared to the lower pressures [10], the observation time is limited mostly by the time of recording. In other words, torsions could be a persistent feature of a plasma crystal experiment (even after preliminary "purification" [14]), and therefore are worthy of study and potential use as a diagnostic tool.…”

Section: MMmentioning

confidence: 99%

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Spontaneous formation and spin of particle pairs in a single-layer complex plasma crystal

Nosenko¹,

Zhdanov²,

Thomas³

et al. 2015

EPL

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In an experiment with a single-layer plasma crystal, spontaneous pairing of particles was observed upon a sudden reduction of the discharge power. The pairs were oriented vertically with the upper particle above the crystal layer and the lower particle beneath it, the pair size was about 0.2 mm. The pairs were spinning around their vertical axis with the upper particle leading and the lower one following it; the rotation speed was 10-13 Hz. Spinning particle pairs disturbed the plasma crystal through interaction with their neighbors. Upon further reduction of the discharge power, the spinning pairs proliferated in the plasma crystal and eventually it melted. The experiment was performed with micron-size polymer particles suspended in the radio-frequency (rf) argon plasma at a pressure of 157 mtorr. We propose a theoretical model of a spinning particle pair based on the plasma wake effect. Spinning particle pairs can be used as a diagnostic tool for plasma wakes or as a generic model of a 2D system of vortices.

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“…Discussion. It is expected that the extra particle floats above the crystal because it has a slightly smaller mass than the other particles [39]. Varying the mass (and charge) of the extra particle may yield further conclusions regarding the mass ratios in experiments.…”

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Wake-Mediated Propulsion of an Upstream Particle in Two-Dimensional Plasma Crystals

et al. 2017

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The wake-mediated propulsion of an "extra" particle in a channel of two neighboring rows of a two-dimensional plasma crystal, observed experimentally by Du et al. [Phys. Rev. E 89, 021101(R) (2014)], is explained in simulations and theory. We use the simple model of a pointlike ion wake charge to reproduce this intriguing effect in simulations, allowing for a detailed investigation and a deeper understanding of the underlying dynamics. We show that the nonreciprocity of the particle interaction, owing to the wake charges, is responsible for a broken symmetry of the channel that enables a persistent self-propelled motion of the extra particle. We find good agreement of the terminal extra-particle velocity with our theoretical considerations and with experiments.

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Spontaneous pairing and cooperative movements of micro-particles in a two dimensional plasma crystal

Cited by 9 publications

References 73 publications

Dynamics of spinning particle pairs in a single-layer complex plasma crystal

Dynamics of spinning particle pairs in a single-layer complex plasma crystal

Spontaneous formation and spin of particle pairs in a single-layer complex plasma crystal

Wake-Mediated Propulsion of an Upstream Particle in Two-Dimensional Plasma Crystals

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