Monthly Archives: June 2015

Photoemission Circular Dichroism and Spin Polarization of the Topological Surface States in Ultrathin Bi_{2} Te_{3} Films

Author(s): C.-Z. Xu, Y. Liu, R. Yukawa, L.-X. Zhang, I. Matsuda, T. Miller, and T.-C. Chiang

The complex behavior of photoemission in topological insulators is a result of quantum interference involving three photoemission channels according to a b i n i t i o calculations.

[Phys. Rev. Lett. 115, 016801] Published Tue Jun 30, 2015

The dust acoustic waves in three dimensional scalable complex plasma. (arXiv:1506.08686v1 [physics.plasm-ph])

Dust acoustic waves in the bulk of a dust cloud in complex plasma of low pressure gas discharge under microgravity conditions are considered. The dust component of complex plasma is assumed a scalable system that conforms to the ionization equation of state (IEOS) developed in our previous study. We find singular points of this IEOS that determine the behavior of the sound velocity in different regions of the cloud. The fluid approach is utilized to deduce the wave equation that includes the neutral drag term. It is shown that the sound velocity is fully defined by the particle compressibility, which is calculated on the basis of the scalable IEOS. The sound velocities and damping rates calculated for different 3D complex plasmas both in ac and dc discharges demonstrate a good correlation with experimental data that are within the limits of validity of the theory. The theory provides interpretation for the observed independence of the sound velocity on the coordinate and for a weak dependence on the particle diameter and gas pressure. Prognostic estimates are made for the ongoing PK 4 experiment.

Wave modes in shear-deformed two-dimensional plasma crystals

Author(s): A. V. Ivlev, T. B. Röcker, L. Couëdel, V. Nosenko, and C.-R. Du

A theory of wave modes in shear-deformed two-dimensional plasma crystals is presented. Modification of the dispersion relations upon the pure and simple shear, and the resulting effect on the onset of the mode-coupling instability, are studied. In particular, it is explained why the velocity fluctua...

[Phys. Rev. E 91, 063108] Published Thu Jun 25, 2015

Modified Enskog kinetic theory for strongly coupled plasmas

Author(s): Scott D. Baalrud and Jérôme Daligault

Concepts underlying the Enskog kinetic theory of hard-spheres are applied to include short-range correlation effects in a model for transport coefficients of strongly coupled plasmas. The approach is based on an extension of the effective potential transport theory [S. D. Baalrud and J. Daligault, P...

[Phys. Rev. E 91, 063107] Published Wed Jun 24, 2015

Equilibration Rates in a Strongly Coupled Nonconformal Quark-Gluon Plasma

Author(s): Alex Buchel, Michal P. Heller, and Robert C. Myers

We initiate the study of equilibration rates of strongly coupled quark-gluon plasmas in the absence of conformal symmetry. We primarily consider a supersymmetric mass deformation within N = 2 * gauge theory and use holography to compute quasinormal modes of a variety of scalar operators, as well as the...

[Phys. Rev. Lett. 114, 251601] Published Tue Jun 23, 2015

Dusty plasma cavities: Probe-induced and natural

Author(s): B. J. Harris, L. S. Matthews, and T. W. Hyde

The dust particles contained in a complex plasma can form two-dimensional crystals, and the authors experimentally study cavities formed in these crystals. They show that cavities that are produced by positively and negatively charged probes, and those that are naturally occurring, are due to three different mechanisms.

[Phys. Rev. E 91, 063105] Published Mon Jun 22, 2015

Effect of dust particle polarization on scattering processes in complex plasmas

Screened interaction potentials in dusty plasmas taking into account the polarization of dust particles have been obtained. On the basis of screened potentials scattering processes for ion-dust particle and dust particle-dust particle pairs have been studied. In particular, the scattering cross section is considered. The scattering processes for which the dust grain polarization is unimportant have been found. The effect of zero angle dust particle-dust particle scattering is predicted.

Effect of anisotropic dust pressure and superthermal electrons on propagation and stability of dust acoustic solitary waves

Employing the reductive perturbation technique, Zakharov–Kuznetzov (ZK) equation is derived for dust acoustic (DA) solitary waves in a magnetized plasma which consists the effects of dust anisotropic pressure, arbitrary charged dust particles, Boltzmann distributed ions, and Kappa distributed superthermal electrons. The ZK solitary wave solution is obtained. Using the small-k expansion method, the stability analysis for DA solitary waves is also discussed. The effects of the dust pressure anisotropy and the electron superthermality on the basic characteristics of DA waves as well as on the three-dimensional instability criterion are highlighted. It is found that the DA solitary wave is rarefactive (compressive) for negative (positive) dust. In addition, the growth rate of instability increases rapidly as the superthermal spectral index of electrons increases with either positive or negative dust grains. A brief discussion for possible applications is included.

Measurement of the speed of sound by observation of the Mach cones in a complex plasma under microgravity conditions. (arXiv:1411.7641v5 [physics.plasm-ph] UPDATED)

We report the first observation of the Mach cones excited by a larger microparticle (projectile) moving through a cloud of smaller microparticles (dust) in a complex plasma with neon as a buffer gas under microgravity conditions. A collective motion of the dust particles occurs as propagation of the contact discontinuity. The corresponding speed of sound was measured by a special method of the Mach cone visualization. The measurement results are incompatible with the theory of ion acoustic waves. The estimate for the pressure in a strongly coupled Coulomb system and a scaling law for the complex plasma make it possible to derive an evaluation for the speed of sound, which is in a reasonable agreement with the experiments in complex plasmas.

Influence of system temperature on the micro-structures and dynamics of dust clusters in dusty plasmas

Influence of the system temperature on the micro-structures and dynamics of dust clusters in dusty plasmas is investigated through laboratory experiment and molecular dynamics simulation. The micro-structures, defect numbers, and pair correlation function of the dust clusters are studied for different system temperatures. The dust grains' trajectories, the mean square displacement, and the corresponding self-diffusion coefficient of the clusters are calculated for different temperatures for illustrating the phase properties of the dust clusters. The simulation results confirm that with the increase in system temperature, the micro-structures and dynamics of dust clusters are gradually changed, which qualitatively agree with experimental results.