Lasers have been used extensively to manipulate matter in a controlled way ? from single atoms and
molecules up to macroscopic materials. They are particularly valuable for the analysis and control
of mesoscopic systems such as few-particle clusters. Here we report on recent work on finite size
complex (dusty) plasma systems. These are unusual types of clusters with a very strong
inter-particle interaction so that, at room temperature, they are practically in their ground state.
Lasers are employed as a tool to achieve excited states and phase transitions. The most attractive
feature of dusty plasmas is that they allow for a precise diagnostic with single-particle
resolution. From such measurements, the structural properties of finite two-dimensional (2D)
clusters and three-dimensional (3D) spherical crystals in nearly harmonic traps?so-called Yukawa
balls?have been explored in great detail. Their structural features?the shell compositions and the
order within the shells?ha...
In a non-ideal classical Coulomb one-component plasma (OCP) all thermodynamic
properties are known to depend only on a single parameter -- the coupling
parameter $\Gamma$. In contrast, if the pair interaction is screened by
background charges (Yukawa OCP) the thermodynamic state depends, in addition,
on the range of the interaction via the screening parameter $\kappa$. How to
determine in this case an effective coupling parameter has been a matter of
intensive debate. Here we propose a consistent approach for defining and
measuring the coupling strength in Coulomb and Yukawa OCPs based on a
fundamental structural quantity, the radial pair distribution function (RPDF).
The RPDF is often accessible in experiments by direct observation or indirectly
through the static structure factor. Alternatively, it is directly computed in
theoretical models or simulations. Our approach is based on the observation
that the build-up of correlation from a weakly coupled system proceeds in two
steps: First, a monotonically increasing volume around each particle becomes
devoid of other particles (correlation hole), and second (upon further increase
of the coupling), a shell structure emerges around each particle giving rise to
growing peaks of the RPDF. Using molecular dynamics simulation, we present a
systematic study for the dependence of these features of the RPDF on $\Gamma$
and $\kappa$ and derive a simple expression for the effective coupling
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The results of a theoretical investigation of an ultracold, neutral plasma
composed of equal mass positive and negative charges are reported. In our
simulations, the plasma is created by the fast dissociation of a neutral
particle. The temperature of the plasma is controlled by the relative energy of
the dissociation. We studied the early time evolution of this system where the
initial energy was tuned so that the plasma is formed in the strongly coupled
regime. In particular, we present results on the temperature evolution and
three body recombination. In the weakly coupled regime, we studied how an
expanding plasma thermalizes and how the scattering between ions affects the
expansion. Because the expansion causes the density to drop, the velocity
distribution only evolves for a finite time with the final distribution
depending on the number of particles and initial temperature of the plasma.
Author(s): J. Goldwin, B. Prasanna Venkatesh, and D. H. J. O’Dell
We predict that an atomic Bose-Einstein condensate strongly coupled to an intracavity optical lattice can undergo resonant tunneling and directed transport when a constant and uniform bias force is applied. The bias force induces Bloch oscillations, causing amplitude and phase modulation of the latt...
[Phys. Rev. Lett. 113, 073003] Published Wed Aug 13, 2014
In this report, the investigation of the properties of dust acoustic (DA) solitary wave propagation in an adiabatic dusty plasma including the effect of the non-thermal ions and trapped electrons is presented. The reductive perturbation method has been employed to derive the modified Korteweg–de Vries (mK-dV) equation for dust acoustic solitary waves in a homogeneous, unmagnetized, and collisionless plasma whose constituents are electrons, singly charged positive ions, singly charged negative ions, and massive charged dust particles. The stationary analytical solution of the mK-dV equation is numerically analyzed and where the effect of various dusty plasma constituents DA solitary wave propagation is taken into account. It is observed that both the ions in dusty plasma play as a key role for the formation of both rarefactive as well as the compressive DA solitary waves and also the ion concentration controls the transformation of negative to positive potentials of the waves.
Sheath formation is studied for collisional plasma in presence of dust. In common laboratory plasma, the dust acquires negative charges because of high thermal velocity of the electrons. The usual dust charging theory dealing with the issue is that of the Orbit Motion Limited theory. However, the theory does not find its application when the ion neutral collisions are significantly present. An alternate theory exists in literature for collisional dust charging. Collision is modeled by constant mean free path model. The sheath is considered jointly with the bulk of the plasma and a smooth transition of the plasma profiles from the bulk to the sheath is obtained. The various plasma profiles such as the electrostatic force on the grain, the ion drag force along with the dust density, and velocity are shown to vary spatially with increasing ion neutral collision.
Author(s): A. Altland, B. Béri, R. Egger, and A. M. Tsvelik
We study the multichannel Kondo impurity dynamics realized in a mesoscopic superconducting island connected to metallic leads. The effective “impurity spin” is nonlocally realized by Majorana bound states and strongly coupled to lead electrons by non-Fermi liquid correlations. We explore the spin dy...
[Phys. Rev. Lett. 113, 076401] Published Mon Aug 11, 2014
Author(s): Péter Magyar, Zoltán Donkó, Gabor J. Kalman, and Kenneth I. Golden
We compute linear and quadratic static density response functions of three-dimensional Yukawa liquids by applying an external perturbation potential in molecular dynamics simulations. The response functions are also obtained from the equilibrium fluctuations (static structure factors) in the system ...
[Phys. Rev. E 90, 023102] Published Mon Aug 11, 2014
The dynamical response of the strongly coupled dusty plasma medium has recently been described by utilizing the Generalized Hydrodynamic (GHD) model equations. The GHD equations capture the visco-elastic properties of the medium and have been successful in predicting a host of phenomena (e.g., existence of novel transverse shear waves in the fluid medium, modification of longitudinal wave dispersion by elastic effects, etc.) which have found experimental confirmation. In this paper, the nonlinear longitudinal response of the medium governed by GHD equations in strong coupling limit is discussed analytically. The structure of the equations rules out the balance between dispersion and nonlinearity, thereby, forbidding soliton formation. However, a host of new varieties of nonlinear solutions are found to exist, which have singular spatial profiles and yet have conservative properties. For instance, existence of novel conservative shock structures with zero strength is demonstrated, waves whose breaking produces no dissipation in the medium are observed, propagating solutions which produce cusp like singularities can exist and so on. It is suggested that simulations and experiments should look for these novel nonlinear structures in the large amplitude strong coupling limit of longitudinal disturbances in dusty plasmas.