Coupled Coulomb Systems Research Articles

Strongly coupled Coulomb systems: Honoring Ken Golden and Gabor Kalman

Strongly coupled Coulomb systems: Honoring Ken Golden and Gabor Kalman

International Conference on “Strongly Coupled Coulomb Systems” (July 24–29, 2022, Görlitz, Germany)

International Conference on “Strongly Coupled Coulomb Systems” (July 24–29, 2022, Görlitz, Germany)

Electron temperature relaxation in the clusterized ultracold plasmas

Ultracold plasmas are a promising candidate for the creation of strongly coupled Coulomb systems. Unfortunately, the values of the coupling parameter Γe actually achieved after photoionization of the neutral atoms remain relatively small because of the considerable intrinsic heating of the electrons. A conceivable way to get around this obstacle might be to utilize a spontaneous ionization of the ultracold Rydberg gas, where the initial kinetic energies could be much less. However, the spontaneous avalanche ionization will result in a very inhomogeneous distribution (clusterization) of the ions, which can change the efficiency of the electron relaxation in the vicinity of such clusters substantially. In the present work, this hypothesis is tested by an extensive set of numerical simulations. As a result, it is found that despite a less initial kinetic energy, the subsequent relaxation of the electron velocities in the clusterized plasmas proceeds much more violently than in the case of the statistically uniform ionic distribution. The electron temperature, first, experiences a sharp initial jump (presumably, caused by the “virialization” of energies of the charged particles) and, second, exhibits a gradual subsequent increase (presumably, associated with a multi-particle recombination of the electrons at the ionic clusters). As a possible tool to reduce the anomalous temperature increase, we also considered a two-step plasma formation, involving the blockaded Rydberg states. This leads to a suppression of the clusterization due to a quasi-regular distribution of ions. In such a case, according to the numerical simulations, the subsequent evolution of the electron temperature proceeds more gently, approximately with the same rate as in the statistically uniform ionic distribution.

The advent of ab initio simulations of dense plasmas

AbstractWe present the story of full three‐dimensional ab initio simulation techniques of dense plasmas based on the Kohn–Sham realization of the density functional theory, starting from early attempts using the Car–Parrinello method to the most recent approaches based on density matrix. We recall the decisive role played by two experiments, one on the Nova laser and the other at a much smaller scale, with pulsed electrical discharges. We emphasize that the essential roles of the Physics of Non‐Ideal Plasmas (PNP) and Strongly Coupled Coulomb Systems (SCCS) conference series were most results, and simulation tools were presented and discussed under the benevolent presence of Vladimir Fortov.

Inner pressure and energy of a Coulomb system in an electrodynamic trap

The results of calculations of the inner pressure and the energy of strongly coupled Coulomb systems in a Paul trap carried out by means of statistical theory of the liquid state are presented. Pair correlation functions of the Coulomb systems have been obtained. Full energy of the system, internal pressure, and the Coulomb coupling parameter Γ were calculated using the inter‐particle Coulomb potential. The considered system is highly non‐ideal with the coupling parameter of order Γ = 1010.

International Conference “Strongly Coupled Coulomb Systems” Kiel, Germany (July 30th–August 4th, 2017)

Contributions to Plasma PhysicsVolume 58, Issue 2-3 p. 76-81 PREFACE International Conference “Strongly Coupled Coulomb Systems” Kiel, Germany (July 30th–August 4th, 2017) First published: 25 March 2018 https://doi.org/10.1002/ctpp.201790032Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume58, Issue2-3Special Issue: International Conference Strongly Coupled Coulomb Systems July 30th – August 4th, 2017, Kiel, Germany, Part IIFebruary-March 2018Pages 76-81 RelatedInformation

Kinetic theory for strongly coupled Coulomb systems.

The calculation of dynamical properties for matter under extreme conditions is a challenging task. The popular Kubo-Greenwood model exploits elements from equilibrium density-functional theory (DFT) that allow a detailed treatment of electron correlations, but its origin is largely phenomenological; traditional kinetic theories have a more secure foundation but are limited to weak ion-electron interactions. The objective here is to show how a combination of the two evolves naturally from the short-time limit for the generator of the effective single-electron dynamics governing time correlation functions without such limitations. This provides a theoretical context for the current DFT-related approach, the Kubo-Greenwood model, while showing the nature of its corrections. The method is to calculate the short-time dynamics in the single-electron subspace for a given configuration of the ions. This differs from the usual kinetic theory approach in which an average over the ions is performed as well. In this way the effective ion-electron interaction includes strong Coulomb coupling and is shown to be determined from DFT. The correlation functions have the form of the random-phase approximation for an inhomogeneous system but with renormalized ion-electron and electron-electron potentials. The dynamic structure function, density response function, and electrical conductivity are calculated as examples. The static local field corrections in the dielectric function are identified in this way. The current analysis is limited to semiclassical electrons (quantum statistical potentials), so important quantum conditions are excluded. However, a quantization of the kinetic theory is identified for broader application while awaiting its detailed derivation.

A tribute to Dietrich Kremp

Dietrich Kremp (1937–2017) made important contributions to statistical physics, especially quantum statistics, plasma physics, and the physics of electrolytes. He was a recognized member of the strongly coupled Coulomb systems and non‐ideal plasmas communities, and his text books continue to have a profound influence on these fields.

International Conference “Strongly Coupled Coulomb Systems” Kiel, Germany (July 30th–August 4th, 2017)

International Conference “Strongly Coupled Coulomb Systems” Kiel, Germany (July 30^th–August 4^th, 2017)

Experimental investigations of strongly coupled Coulomb systems of diamagnetic dust particles in a magnetic trap under microgravity conditions

A series of experiments on the modernized “Coulomb crystals” setup on board of the International Space Station (ISS) was performed. Formation of a cluster of charged and uncharged particles was observed. Excitation and damping of cluster oscillations, as well as its destruction in the high electric field were investigated. Charges of the particles were evaluated on the basis of their rate of expansion from the cluster. Some conclusions about the cluster structure have been presented.

Towards Stronger Coulomb Coupling in an Ultracold Neutral Plasma

AbstractUltracold neutral plasmas are strongly coupled Coulomb systems that are generated by photoionizing lasercooled atoms close to the ionization threshold. The strong coupling parameter Γ is limited at times later than ∼100 ns by disorder‐induced heating. A recent simulation predicted that higher values of Γ can be realized in ultracold neutral plasmas if the plasma ions are excited to higher ionization states. In this paper we present recent results from an experiment that increases the strong coupling of an ultracold neutral plasma by promoting the plasma ions to the second ionization state. Using laser‐induced fluorescence we map out the ion velocity distribution of the Ca+ ions in a partially doubly ionized plasma and show that the heating due to the second ionization depends on the timing of the second ionization laser pulses. We compare our results to MD simulations, which estimate that Γ increases from approximately 2.5 to 3.6. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Conductivity of warm dense matter including electron-electron collisions.

We present an approach that can resolve the controversy with respect to the role of electron-electron collisions in calculating the dynamic conductivity of dense plasmas. In particular, the dc conductivity is analyzed in the low-density, nondegenerate limit where the Spitzer theory is valid and electron-electron collisions lead to the well-known reduction in comparison to the result considering only electron-ion collisions (Lorentz model). With increasing degeneracy, the contribution of electron-electron collisions to the dc conductivity is decreasing and can be neglected for the liquid metal domain where the Ziman theory is applicable. We give expressions for the effect of electron-electron collisions in calculating the conductivity in the warm dense matter region, i.e., for strongly coupled Coulomb systems at arbitrary degeneracy.

Measurement of the speed of sound by observation of the Mach cones in a complex plasma under microgravity conditions

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.

A Review of Studies on Strongly‐Coupled Coulomb Systems Since the Rise of DFT and SCCS‐1977

AbstractThe conferences on “Strongly Coupled Coulomb Systems” (SCCS) arose from the “Strongly Coupled Plas‐mas” meetings, inaugurated in 1977. The progress in SCCS theory is reviewed in an ‘author‐centered’ frame to limit its scope. Our efforts, i.e., with François Perrot, sought to apply density functional theory (DFT) to SCCS calculations. DFT was then poised to become the major computational scheme for condensed matter physics. The ion‐sphere models of Salpeter and others evolved into useful average‐atom models for finite‐T Coulomb systems, as in Lieberman's Inferno code. We replaced these by correlation‐sphere models that exploit the description of matter via density functionals linked to pair‐distributions. These methods provided practical computational means for studying strongly interacting electron‐ion Coulomb systems like warm‐dense matter (WDM). The staples of SCCS are wide‐ranged, viz., equation of state, plasma spectroscopy, opacity (absorption, emission), scattering, level shifts, transport properties, e.g., electrical and heat conductivity, laser‐ and shock‐created plasmas, their energy relaxation and transient properties etc. These calculations need pseudopotentials and exchange‐correlation functionals applicable to finite‐T Coulomb systems that may be used in ab initio codes, molecular dynamics, etc. The search for simpler computational schemes has proceeded via proposals for orbital‐free DFT, statistical potentials, classical maps of quantum systems using classical schemes like HNC to include strong coupling effects (CHNC). Laughlin's classical plasma map for the fractional quantum Hall effect (FQHE) is a seminal example where we report new results for graphene. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A tribute to pioneers of strongly coupled plasmas: Hugh E. DeWitt, Bernard Jancovici, and Forrest J. Rogers

AbstractThe field of strongly coupled Coulomb systems that stretches from dense plasma, to astrophysics, condensed matter and high energy physics has seen a dramatic development over the last four decades. At the beginning of this process were a few physicists whose work has had a high impact on many exciting developments of the recent years. Among them are Hugh E. DeWitt, Bernard Jancovici and Forrest J. Rogers who passed away in 2013–2014. Their important contributions to the field of strongly coupled Coulomb systems are summarized in this article. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Polarization momentum transfer collision: Faxen-Holtzmark theory and quantum dynamic shielding

The influence of the quantum dynamic shielding on the polarization momentum transport collision is investigated by using the Faxen-Holtzmark theory in strongly coupled Coulomb systems. The electron-atom polarization momentum transport cross section is derived as a function of the collision energy, de Broglie wavelength, Debye length, thermal energy, and atomic quantum states. It is found that the dynamic shielding enhances the scattering phase shift as well as the polarization momentum transport cross section. The variation of quantum effect on the momentum transport collision due to the change of thermal energy and de Broglie wavelength is also discussed.

Heterogeneous crystallization in colloids and complex plasmas: the role of binary mobilities

Both charged colloidal suspensions and complex (dusty) plasmas represent classical many-body strongly coupled Coulomb systems. Here we discuss their basic properties and focus on their heterogeneous crystallization from an undercooled melt. In particular, a model with different mobilities is proposed which is realizable in binary mixtures of charged particles. Within this binary-mobility model, the crystallization behaviour near a structured wall is explored by Brownian dynamics computer simulations. As a result, the propagation velocity of the crystal–fluid interface is a nonmonotonic function of the mobility ratio (if expressed in terms of an averaged mobility).

Preface: Contrib. Plasma Phys. 10/2009

AbstractThe XIII International Conference on Physics of Non‐Ideal Plasmas was held in Chernogolovka, Russia, from September 13–18, 2009. The Conference continues a traditional series of meetings devoted to new theoretical and experimental results on the physics of dense non‐plasmas: Martzlow‐Garwitz, 1980; Wustrow, 1982; Biesenthal, 1984; Greifswald, 1986; Wustrow, 1988; Gosen, 1991; Markgrafenheide, 1993; Binz, 1995; Rostock, 1998; Greifswald, 2000; Valencia, 2003; Darmstadt, 2006.The results of these Conferences have been published in the journal “Contributions to Plasma Physics”. We thank the Editors to give also for the present Conference the possibility for publication of new results in the physics of non‐ideal plasmas.The following questions are covered: statistical physics and mathematical modeling (including simulation) of strongly coupled Coulomb systems, equilibrium properties and equation of state of dense plasmas, kinetics, transport and optical properties of dense Coulomb systems, dense hydrogen, laser and heavy‐ion‐produced plasmas, dense astrophysical plasmas, phase transitions in plasmas and fluids, dusty plasmas.More than 150 contributions were submitted and the program committee chose 5 papers to be presented as invited topical lectures and 43 papers to be presented as oral lectures. In additions, 10 oral presentations were presented on a young scientists special session and 61 posters were presented in two poster sessions. We were pleased to welcome 110 participants from 47 scientific organizations representing 16 countries in Chernogolovka at the conference.The articles in this issue are based on the talks at the PNP13 conference providing original research results. All articles have undergone a strict anonymous scientific review by experts in the field assuring a high quality of this issue. We thank to all colleagues who contributed to this issue as an author, but also as a referee.Finally, we would like to thank the sponsors for the generous support of the conference.The EditorsChernogolovka, Rostock, November 2009

Strongly Coupled Coulomb Systems

Strongly Coupled Coulomb Systems

Fast-Projectile Stopping Power of Quantal Multicomponent Strongly Coupled Plasmas

The Bethe-Larkin formula for the fast-projectile stopping power is extended to multicomponent plasmas. The results are to contribute to the correct interpretation of the experimental data, which could permit us to test existing and future models of thermodynamic, static, and dynamic characteristics of strongly coupled Coulomb systems.