Towards thermal equilibrium in the Bose-Einstein condensation of microcavity polaritons

By comparing a kinetic and a thermal-equilibrium theory of polariton Bose-Einstein condensation, we study under what conditions the dynamical condensation under steady-state non-resonant pumping can approach thermal equilibrium. In particular, we study the dependence on two material parameters: the vacuum-field Rabi-splitting and the polariton radiative lifetime. When increasing the Rabi splitting, condensation takes place under strong non-equilibrium conditions, with dominating quantum fluctuations. Increasing the polariton lifetime above 10 ps at moderate Rabi splitting, instead, produces a quasi-equilibrium condensate at low exciton density, consistently with the picture of a weakly interacting Bose gas.     

Formation of nickel extended surface upon quasi-equilibrium steady-state condensation

It has been established that nickel condensates in the form of low-dimensional porous systems can be obtained at quasi-equilibrium steady-state condensation. On the basis of the structural-morphological characteristics obtained at different condensate growth stages, it has been shown that porosity formation occurs without coalescence upon reorientation of the condensed flux in the region of the initial cluster aggregation and also when homonucleation of new clusters takes place in the regions of the initial cluster intergrowth.     

Self-organization of plasma-condensate quasi-equilibrium systems

Physics of the Solid State - The steady-state regime of condensation under conditions close to the phase equilibrium is shown to be provided by the self-organization of the plasma-condensate...     

Self-organization and supramolecular chemistry of protein films from the nano-to the macroscale

Experimental data obtained with optical, polarization, scanning electron, and confocal laser microscopes reveal a previously unknown supramolecular modification of protein self-organization (“protos”). This modification arises upon condensation in the open nonequilibrium water-protein system. The process gives rise to the liquid crystal phase of nanostructured eddylike protos films epitaxially growing on the nano-and macrolevels. The model of protein spontaneous self-organization allows one to visualize and study the nonlinear dynamics of condensation and self-organization of protein films with a supramolecular configuration on the nano-and macroscale under abiotic and biotic conditions. This model may help in creating an atlas for protein identification, as well as for diagnostics of pathogenic processes in the living organism that disturb protein self-organization.     

Elimination of the intermediate colloidal product in models of periodic precipitation patterns

Periodic precipitation phenomena constitute a good example of self-organization in chemical systems. In order to simplify models of periodic precipitation as much as possible, we propose here two approximate schemes that eliminate the dynamics of the intermediate colloidal product explicitly: a steady-state elimination scheme and a local chemical equilibrium one.     

Phase diagram of electron-hole systems: Interplay between exciton Mott transition and quantum pair condensation

Quasi-thermal-equilibrium states of electron-hole (e-h) systems in photoexcited insulators are studied from a theoretical viewpoint, stressing the exciton Bose-Einstein condensation (BEC), the e-h BCS-type pair-condensed state, and the exciton Mott transition between an insulating exciton/biexciton gas phase and a metallic e-h plasma phase. We determine the quasi-equilibrium phase diagram of the e-h system at zero and finite temperatures with applying the dynamical mean-field theory (DMFT) to the e-h Hubbard model with both repulsive and attractive on-site interactions. Effects of inter-site interactions on the exciton Mott transition are also clarified with applying the extended DMFT to the extended e-h Hubbard model.     

Formation of nanosystems under near-equilibrium copper condensation in an ultrapure inert medium

Mechanisms of the self-organization of nanosystems at the condensation of the extremely weak steady flows of copper vapors obtained in magnetron sputtering in an ultrapure argon are studied. It is shown that the free-energy minimization near equilibrium condensation creates prerequisites for the self-organization of statistically homogeneous layers of nanoclusters and determines the transition to the formation of nanosystems in the form of fractal networks.     

Oxidation of CO on Pt and Pd: I. Theory

The kinetics of CO oxidation on the metals Pt and Pd have been analyzed theoretically within the framework of a model that incorporates both the Eley-Rideal and Langmuir-Hinshelwood mechanisms. The model takes into account the dissociative adsorption of oxygen on adjacent vacant surface sites. Exact solutions to the differential equations describing the model have been obtained for (a) the steady-state characterized by constant temperature and pressure, and (b) a quasi-equilibrium state in which one of the reactant gas phase pressures is modulated with frequency ω.     

On the type of a phase transition in the system of exciton polaritons in an optical microcavity

The type of a phase transition in the quasi-equilibrium system of exciton polaritons in a two-dimensional optical microcavity has been analyzed. It has been shown that, although the system contains two types of bosons undergoing mutual transformations into each other, only one phase transition to the superfluid state with the quasilong-range order occurs in the two-dimensional system. This phase transition is a Kosterlitz-Thouless phase transition. A new physical implementation—excitons in a photon crystal—has been proposed for the Bose condensation of exciton polaritons. The superfluid properties of the ordered phase are discussed, and the superfluid density and Kosterlitz-Thouless transition temperature have been calculated in the low-density approximation.     

The dynamics of cargo driven by molecular motors in the context of asymmetric simple exclusion processes

We consider the dynamics of cargo driven by a collection of interacting molecular motors in the context of an asymmetric simple exclusion process (ASEP). The model is formulated to account for (i) excluded-volume interactions, (ii) the observed asymmetry of the stochastic movement of individual motors and (iii) interactions between motors and cargo. Items (i) and (ii) form the basis of ASEP models and have already been considered to study the behavior of motor density profile [A. Parmeggiani, T. Franosch, E. Frey, Phase Coexistence in driven one-dimensional transport, Phys. Rev. Lett. 90 (2003) 086601-1-086601-4]. Item (iii) is new. It is introduced here as an attempt to describe explicitly the dependence of cargo movement on the dynamics of motors in this context. The steady-state solutions of the model indicate that the system undergoes a phase transition of condensation type as the motor density varies. We study the consequences of this transition to the behavior of the average cargo velocity.     

Condensation in Hamiltonian parametric wave interaction

In the generic Hamiltonian problem of parametric wave interaction, we show theoretically the existence of a sudden transition leading the wave system from completely incoherent states towards highly coherent states. This self-organization process is characterized by a reduction of the nonequilibrium entropy, in contrast with the H theorem of entropy growth inherent to the random phase approximation approach. The mechanism underlying this intriguing condensation process is in essence a reversible nonlinear damping. As a result, the lower the coherence of the initial state, the higher the coherence of the final state.     

On the validity of the Onsager reciprocal relations for simultaneous heat transfer and multi-component diffusion

In this work, the validity of the Onsager reciprocal relations (ORR) for the heat transfer and multi-component diffusion case in the presence of external forces is re-examined. It is shown that the ORR are necessarily fulfilled for this process even if the quasi-equilibrium postulate is applied. Moreover, it is shown that the resistance coefficients for this case are uniquely defined. It is believed that this work could contribute to the further understanding of the ORR.     

Oriented growth of oxygen-free C60 crystallites on silicon substrates

This is the first report of preparation of C₆₀ fullerite films on silicon substrates coated by a layer of natural oxide. The crystallites are about 1 μm in size. The films were found to have an enhanced stability to atmospheric oxygen. The films were obtained by a modified method of discrete evaporation in a quasi-closed volume. The principal features of the method are the quasi-equilibrium condensation conditions, a high substrate temperature (up to 300 °C), and alternation of deposition with recrystallization in a single technological cycle. The method is characterized by high film condensation rates (up to 2000 ?/min) and an economical expenditure of the starting material. A study has been made of the surface structure and morphology, and of the depth profile of the film optical constants and elemental composition. Fiz. Tverd. Tela (St. Petersburg) 41, 354–359 (February 1999)     

Lasing threshold in traps for Bose-condensation of dipolar excitons

We consider exciton recombination lasing in heterostructure traps for Bose–Einstein condensation of dipolar excitons. We show that such structures suit well for class D lasers where cavity decay strongly exceeds polarization decay. We evaluate lasing threshold taking into account specific inhomogeneous broadening of the exciton spectral line owing to Bose–Einstein condensation phenomenon under quasi-equilibrium conditions.It is found that narrowing of the exciton momentum distribution just before the condensation onset considerably lowers lasing threshold. At the same time, it is pointed out that a subsequent formation of condensate itself does not help lasing much. We conclude that it is possible to achieve lasing on polariton modes in nowadays experiments aimed on Bose–Einstein condensation of excitons.     

Formation of nanosystems under near-equilibrium copper condensation in an ultrapure inert medium

Mechanisms of the self-organization of nanosystems at the condensation of the extremely weak steady flows of copper vapors obtained in magnetron sputtering in an ultrapure argon are studied. It is shown that the free-energy minimization near equilibrium condensation creates prerequisites for the self-organization of statistically homogeneous layers of nanoclusters and determines the transition to the formation of nanosystems in the form of fractal networks. Original Russian Text ? V.I. Perekrestov, A.S. Kornyushchenko, Yu.A. Kosminskaya, 2007, published in Pis’ma v Zhurnal éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 12, pp. 879–883.     

Bose–Einstein condensation versus Dicke–Hepp–Lieb transition in an optical cavity

We provide an exact solution for the interplay between Bose–Einstein condensation and the Dicke–Hepp–Lieb self-organization transition of an ideal Bose gas trapped inside a single-mode optical cavity and subject to a transverse laser drive. Based on an effective action approach, we determine the full phase diagram at arbitrary temperature, which features a bi-critical point where the transitions cross. We calculate the dynamically generated band structure of the atoms and the associated suppression of the critical temperature for Bose–Einstein condensation in the phase with a spontaneous periodic density modulation. Moreover, we determine the evolution of the polariton spectrum due to the coupling of the cavity photons and the atomic field near the self-organization transition, which is quite different above or below the Bose–Einstein condensation temperature. At low temperatures, the critical value of the Dicke–Hepp–Lieb transition decreases with temperature and thus thermal fluctuations can enhance the tendency to a periodic arrangement of the atoms.     

On the problem of nucleation (cell formation) in self-organization of protein nanostructures <Emphasis Type="Italic">in vitro</Emphasis> and <Emphasis Type="Italic">in vivo</Emphasis>

No convincing theory or hypothesis concerning the origin of biological cells exists today. Insight into the problem is difficult, because an empiric model of cell origination and division at the crucial phase of life, self-organization of protein nanostructures, is lacking. It has been shown experimentally that protein nanostructures exhibit signs of self-organization when an open far-from-equilibrium protein-water system condenses in vitro. In other words, to be active, protein must be in the nonequilibrium state. Such a form of self-organization is accompanied by nucleation and the formation of defects, which divide the protein film into domains (“cells”) with nuclei. This type of structuring in the nonequilibrium (active) protein may be viewed as a crude empiric model of protein nucleation, since it includes the formation and division (self-organization) of biological cells, the origination of which, in turn, is intimately related to the self-organization of protein at the nanolevel. The reason for the similarity of the basic processes is identical conditions of protein condensation in vitro and in vivo. In both cases, when water evaporates rapidly from an open water-protein system that is far from thermodynamic equilibrium, the conditions necessary for protein nonequilibrium nanostructures be self-organized with nucleation in the form of nucleus-containing “cells” are set.     

Hierarchical condensation near phase equilibrium

A novel mechanism of new phase formation is studied both experimentally and theoretically in the example of quasi-equilibrium stationary condensation in an ion–plasma sputterer. Copper condensates are obtained to demonstrate that a specific network structure is formed as a result of self-assembly in the course of deposition. The fractal pattern related is inherent in the phenomena of diffusion limited aggregation. Condensate nuclei are shown to form statistical ensemble of hierarchically subordinated objects distributed in ultrametric space. The Langevin equation and the Fokker–Planck equation related are found to describe stationary distribution of thermodynamic potential variations at condensation. Time dependence of the formation probability of branching structures is found to clarify the experimental situation.     

Phenomenon of statistical instability of the third type systems—complexity

The problem of the existence and special properties of third type systems has been formulated within the new chaos–self-organization theory. In fact, a global problem of the possibility of the existence of steady-state regimes for homeostatic systems has been considered. These systems include not only medical and biological systems, but also the dynamics of meteorological parameters, as well as the ambient parameters of the environment in which humans are located. The new approach has been used to give a new definition for homeostatic systems (complexity).