Monthly Archives: September 2014

The ion potential in warm dense matter: wake effects due to streaming degenerate electrons. (arXiv:1409.8079v1 [physics.plasm-ph])

The effective dynamically screened potential of a classical ion in a stationary flowing quantum plasma at finite temperature is investigated. This is a key quantity for thermodynamics and transport of dense plasmas in the warm dense matter regime. To compute this potential a linear response description of the electrons via the Mermin dielectric function is utilized with electron-electron collisions taken into account via a relaxation time approximation. The ion potential strongly deviates from the static Yukawa potential exhibiting the familiar oscillatory structure with attractive minima (wake potential). This potential is analyzed in detail for high-density plasmas with values of the Brueckner parameter in the range $0.1 e r_s e 1$, for a broad range of plasma temperature and electron streaming velocity. It is shown that wake effects become weaker with increasing temperature of the electrons. Finally, we obtain the minimal electron streaming velocity for which attraction between ions occurs. This velocity turns out to be less than the electron Fermi velocity. The observed effects should be of high relevance for transport under warm dense matter conditions, in particular for laser-matter interaction, electron-ion temperature equilibration and for stopping power.

Mode-Coupling Instability in a Fluid Two-Dimensional Complex Plasma

Author(s): A. V. Ivlev, S. K. Zhdanov, M. Lampe, and G. E. Morfill

A theory of the mode-coupling instability (MCI) in a fluid two-dimensional complex plasma is developed. In analogy to the point-wake model of the wake-mediated interactions commonly used to describe MCI in two-dimensional crystals, the layer-wake model is employed for fluids. It is demonstrated that...

[Phys. Rev. Lett. 113, 135002] Published Tue Sep 23, 2014

A temporal multi-scale algorithm for efficient fluid modeling of a one-dimensional gas discharge

In this study, we present a temporal multi-scale algorithm (TMA) for efficient fluid modeling of a one-dimensional gas discharge with complex plasma chemistry. A helium dielectric barrier discharge driven by a power source with a frequency of 25 kHz is used as an example to demonstrate the superior capability of the TMA in accelerating fluid modeling simulations, while maintaining the same accuracy as compared to lengthy benchmarking fluid modeling using a single time-scale approach. The plasma chemistry considers 36 species and 121 reaction channels, which include some impurities such as nitrogen (25 ppm), oxygen (10 ppm) and water vapor (1 ppm), in addition to the helium itself. The results show that the runtime using the TMA can be dramatically reduced to 4% (25 times faster) with a relative difference of spatially averaged number densities generally less than 1% for all species between the TMA and the benchmarking cases when five initial cycles, five supplementary cycles and ...

Painlevé analysis, auto-Bäcklund transformation, and new exact solutions for Schamel and Schamel-Korteweg-de Vries-Burger equations in dust ion-acoustic waves plasma

A theoretical investigation of dust-acoustic solitary waves in one-dimensional, collisionless, and unmagnetized dusty plasma consisting of ion fluid, trapped as well as free electrons, and charge fluctuating immobile dust particles is considered. The nonlinear dynamics of dust ion-acoustic waves, whose phase speed is much smaller (larger) than the electron (ion) thermal speed, propagating in such a dusty plasma system is investigated. The reductive perturbation method is employed to reduce the basic set of fluid equations to the Schamel and Schamel-Korteweg-de Vries-Burger (S-KdVB) equations. The Schamel and Schamel-KdVB equations are shown to be non-integrable using Painlevé analysis. The Bäcklund transformations and some new exact solutions are formally derived. Finally, we discussed the results in this paper.

Mode coupling and resonance instabilities in quasi-two-dimensional dust clusters in complex plasmas

Author(s): Ke Qiao, Jie Kong, Jorge Carmona-Reyes, Lorin S. Matthews, and Truell W. Hyde

Small quasi-two-dimensional dust clusters consisting of three to eleven particles are formed in an argon plasma under varying rf power. Their normal modes are investigated through their mode spectra obtained from tracking the particles’ thermal motion. Detailed coupling patterns between their horizo...

[Phys. Rev. E 90, 033109] Published Tue Sep 16, 2014

Quasilongitudinal soliton in a two-dimensional strongly coupled complex dusty plasma in the presence of an external magnetic field

Author(s): Samiran Ghosh

The propagation of a nonlinear low-frequency mode in two-dimensional (2D) monolayer hexagonal dusty plasma crystal in presence of external magnetic field and dust-neutral collision is investigated. The standard perturbative approach leads to a 2D Korteweg-de Vries (KdV) soliton for the well-known du...

[Phys. Rev. E 90, 033108] Published Mon Sep 15, 2014

The acoustic instabilities in magnetized collisional dusty plasmas

The present work investigates the wave propagation in collisional dusty plasmas in the presence of electric and magnetic field. It is shown that the dust ion-acoustic waves may become unstable to the reactive instability whereas dust-acoustic waves may suffer from both reactive and dissipative instabilities. If the wave phase speed is smaller than the plasma drift speed, the instability is of reactive type whereas in the opposite case, the instability becomes dissipative in nature. Plasma in the vicinity of dust may also become unstable to reactive instability with the instability sensitive to the dust material: dielectric dust may considerably quench this instability. This has implications for the dust charging and the use of dust as a probe in the plasma sheath.

Electrostatic spin control in multi-barrier nanowires

We demonstrate that a consistent breakdown of the standard even–odd filling scheme in the Coulomb blockade regime can be easily obtained in a quantum dot containing two wells strongly coupled by a very transparent barrier. By exploiting a multi-gate configuration, we prove that a partial filling of nearly degenerate orbitals can be controlled electrostatically. Singlet–triplet spin transitions are demonstrated by low-temperature magneto-transport measurements.

Dust-acoustic solitary waves and shocks in strongly coupled quantum plasmas. (arXiv:1409.1982v1 [physics.plasm-ph])

We investigate the propagation characteristics of electrostatic dust-acoustic (DA) solitary waves and shocks in a strongly coupled dusty plasma consisting of intertialess electrons and ions, and strongly coupled inertial charged dust particles. A generalized viscoelastic hydrodynamic model with the effects of electrostatic dust pressure associated with the strong coupling of dust particles, and a quantum hydrodynamic model with the effects of quantum forces associated with the Bohm potential and the exchange-correlation potential for electrons and ions are considered. Both the linear and weakly nonlinear theory of DA waves are studied by the derivation and analysis of dispersion relations as well as Korteweg-de Vries (KdV) and KdV-Burgers (KdVB)-like equations. It is shown that in the kinetic regime ($\omega\tau_m\gg1$, where $\omega$ is the wave frequency and $\tau_m$ is the viscoelastic relaxtation time), the amplitude of the DA solitary waves decays slowly with time with the effect of a small amount of dust viscosity. However, the DA shock-like perturbations can be excited in the hydrodynamic regime with $\omega\tau_ml1$. The analytical and numerical solutions of the KdV and KdVB equations are also presented and analyzed with the system parameters.

Effective Potential and Interdiffusion in Binary Ionic Mixtures. (arXiv:1409.1407v1 [astro-ph.SR])

We calculate interdiffusion coefficients in a two-component, weakly or strongly coupled ion plasma (gas or liquid, composed of two ion species immersed into a neutralizing electron background). We use an effective potential method proposed recently by Baalrud and Daligaut [PRL, 110, 235001, (2013)]. It allows us to extend the standard Chapman-Enskog procedure of calculating the interdiffusion coefficients to the case of strong Coulomb coupling. We compute binary diffusion coefficients for several ionic mixtures and fit them by convenient expressions in terms of the generalized Coulomb logarithm. These fits cover a wide range of plasma parameters spanning from weak to strong Coulomb couplings. They can be used to simulate diffusion of ions in ordinary stars as well as in white dwarfs and neutron stars.