Bounds on the reflectivity of two-component composite

Bounds on the effective permittivity circumscribe 2D area in the complex plane representing possible values of permittivity. It is shown that the corresponding possible values of reflectivity occur within the interval determined by the lowest and the highest reflectivity value, which represent minimum and maximum values of reflectivity found at the permittivity bounds.     

Rigorous bounds for the complex dielectric constant of a two-component composite

Rigorous bounds are systematically derived for the bulk effective dielectric constant of a two-phase composite material ε_e under various assumptions about the available information. The bounds are drawn for some special cases in the complex ε_e-plane. The question of optimality of the bounds and their connection to solvable microgeometries is discussed. It is shown how linear programming theory can be used to aid in the derivation of these bounds.     

A highly efficient white-light-emitting diode based on a two-component polyfluorene/quantum dot composite

Organic light-emitting diodes (OLEDs) are attracting great interest of the scientific community and industry because they can be grown on flexible substrates using relatively simple and inexpensive technologies (solution processes). However, a problem in the fabrication of white OLEDs is that it is difficult to achieve a balance between the intensities of individual emission components in the blue, green, and red spectral regions. In this work, we try to solve this problem by creating a two-component light-emitting diode based on modified polyfluorene (PF-BT), which efficiently emits in the blue–green region, and CdSe/ZnS/CdS/ZnS semiconductor quantum dots emitting in the orange–red region with a fluorescence quantum yield exceeding 90%. By changing the mass ratio of components in the active light-emitting composite within 40–50%, it is possible to transform the diode emission spectrum from cold to warm white light without loss of the diode efficiency. It is very likely that optimization of the morphology of multilayer light-emitting diodes will lead to further improvement of their characteristics.     

Expansion of a two-component plasmoid in a vacuum

Numerical integration of the equations of two-fluid hydrodynamics is used to solve the problem of the one-dimensional expansion in a vacuum of a quasineutral plasmoid, consisting of a mixture of ions of different charges and masses. A space-time picture of the change in me hydrodynamic quantities and the electric field is obtained, and the effect of the ion mass and charge is investigated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 66–71, February, 1978.     

Acoustic plasmons in a two-component Fermi system

The dispersion and line width of the longitudinal collective modes of a two-component degenerate Fermi-system (T=0) are obtained from the zeros of the dielectric function (q,). The basis of our theory are kinetic equations for the distribution function including elastic electron-impurity scattering. Our results area) there is only one acoustic branchb) this mode is overdamped forq0, andc) acoustic plasmons contribute only little to the energy loss-function (or the screened electron-ion and electron-electron potential).     

Melt-crystal phase transition in a two-component system

The melt-crystal phase transition in a two-component system is described by a generalized Ornstein-Zernicke equation for one- and two-particle distribution functions. The jump in the density δn under melt crystallization is a small parameter. The desired distribution functions are found as δn power series. The two-particle distribution function for the melt along its crystallization line is chosen as a zeroth approximation. Institute of Applied Physics at the Irkutsk University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 54–61, February 2000.     

Vortex sublattice melting in a two-component superconductor

We consider the vortices in a superconductor with two individually conserved condensates in a finite magnetic field. The ground state is a lattice of cocentered vortices in both order parameters. We find two phase transitions: (i) a "vortex sublattice melting" transition where vortices in the field with lowest phase stiffness ("light vortices") lose cocentricity with the vortices with large phase stiffness ("heavy vortices"), entering a liquid state (the structure factor of the light vortices vanishes continuously; this transition is in the 3Dxy universality class); (ii) a first-order melting transition of the lattice of heavy vortices, in a liquid of light vortices.     

Dark solitons in a two-component Bose-Einstein condensate

The creation and interaction of dark solitons in a two-component Bose-Einstein condensate is investigated. For a miscible case, the interaction of dark solitons in different components is studied. Various possible scenarios are presented, including the formation of a soliton-soliton bound pair. We also analyze the soliton propagation in the presence of domains, and show that a dark soliton can be transferred from one component to the other at the domain wall when it exceeds a critical velocity. For lower velocities multiple reflections within the domain are observed, where the soliton is evaporated and accelerated after each reflection until it finally escapes from the domain.     

Forward-backward multiplicity distribution in a two-component model

We calculate stochastic quantities in a two-component model which is a product of a negative binomial and a Poisson distribution. The generating function and the KNO scaling function are obtained. A formula for the forward-backward (F-B) multiplicity correlation is derived from the generating function. We consider the case in which particles are produced in pairs and compare with experiment.     

Entropy of a two-component fluid in a square-well model

An analytical expression valid for two approximations, notably, the random phase approximation (RPA) and the mean spherical approximation (MSA), is derived for entropy of a two-component system with the pair potential of a square well (SW). This expression is applied to calculate the excess entropy of mixing of the Na-K and Na-Cs equiatomic compositions. It is shown that the use of the SW model leads to better results than the application of the hard-sphere model. The MSA gives better convergence with the experiment compared with the RPA.     

Exact results for correlations in a two-component log-gas

A study of the one-dimensional lattice gas of positive and negative charges interacting via the logarithmic potential is continued. The two-particle distribution functions are evaluated exactly at the couplings=2 and 4. It is proved that the=4 isotherm exhibits an insulator-conductor phase transition at the reduced density 1/2, and the scaling behavior of the correlations near this critical point is given. Similarities of the conjectured phase diagram with that of a one-dimensional one-component log-gas in a periodic potential are noted.     

Superfluid-superfluid phase transitions in a two-component Bose-Einstein condensate

Depending on the Hamiltonian parameters, two-component bosons in an optical lattice can form at least three different superfluid phases in which both components participate in the superflow: a (strongly interacting) mixture of two miscible superfluids (2SF), a paired superfluid (PSF) vacuum, and (at a commensurate total filling factor) the super-counter-fluid (SCF) state. We study the universal properties of the 2SF-PSF and 2SF-SCF quantum phase transitions and show that (i) they can be mapped onto each other and (ii) their universality class is identical to the (d+1)-dimensional normal-superfluid transition in a single-component liquid. The finite-temperature 2SF-PSF(SCF) transitions and the topological properties of 2SF-PSF(SCF) interfaces are also discussed.     

Induced long-time correlations in a two-component lattice gas

The distinguishability of at least two species of particles in the classical lattice gas with no interactions except hard-core exclusion entails additional interparticle correlations. A nonlinear mixing flow appears and manifests itself most pronouncedly in the case of signi- ficant difference between mobilities of species. It may cause induced correlations for a slow component mediated by a fast one. In the quasi-one-dimensional case, the long-time correlations are demonstrated to take place in a slow component, which is similar to the hydrodynamic correlations between colloidal particles. In the adiabatic approximation, these correlations may come into play only in the non-equilibrium case with the flow of a fast component present in the system.     

Conductivity of two-component systems in a magnetic field

The influence of a magnetic field on the effective conductivity of a system with a chessboard structure is studied under conditions of the Hall effect. It is shown that in this case a new physical effect occurs, involving an oscillatory dependence of the charge density at the interfaces on passage through the bifurcation point. The system possesses considerable magnetoresistance.     

The Andreev-Bashkin effect in a two-component Bose gas

A microscopic theory is developed for the Andreev-Bashkin effect in a superfluid two-component weakly nonideal Bose gas. An expression is obtained for the matrix of superfluid densities in the general case of two gases with different densities, particle masses, and scattering lengths. A method for the observation of a drag between superfluid components is proposed.     

On a two-component theory of fermions

In this article the well known Klein paradox is investigated for fermions in the Volkovyskii representation. It is shown that a transition into an antiparticle state is possible upon the passage of a particle from the region with U(x) = 0 into the region with U(x) > mc².Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 120–122, February, 1974.