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The two-component mixture of Bose particles with short-range pairwise interaction at finite temperatures in three dimensions is considered. Particularly we examine, by means of the large-$N$ expansion technique, the stability of mixed state below the Bose-Einstein transition point and the temperature dependence of the condensate density for symmetric mixture of Bose gases. The presented analysis reveals the importance of finite-temperature excitations of the non-condensed particles in formation of the phase diagram of two-component Bose systems., 6 pages, 5 figures

The electric properties of complex hybrid structure formed by insertion of Samarium (III) Chloride into mesoporous silica matrix were investigated. The character of impedance, loss tangent and permittivity dependences on frequency was determined under standard conditions, illumination and in magnetic field, and conditions under which the permittivity is below unit were established. The thermogalvanic effect was observed with use of method of thermostimulated depolarization and its mechanisms were analyzed. The theory for thermogalvanic effect, which explains its connection with dielectric permittivity, was developed.

We have discovered a huge enhancement of the supercapacity (up to 4 times) under sun illumination of electrodes fabricated from cavitated nanoporous carbon being carbonized from an iodine doped β–cyclodexryn. This effect was achieved even without a frequently used KOH treatment and is caused by enhancement of effective activated surfaces. The synthesized cavitated nanoporous carbon exhibits principally different accumulative features at the carbon/electrolyte interface. Relationship between the porous structure, electronic properties of supramolecular nanoporous carbon and enhanced supercapacitance is explored. The impedance spectroscopy measurements (Nyquist diagram) apparently suggest a capacitance mechanism for the energy accumulation. Enhancement of the supercapacity is explained by light-generated carriers in low-dimensional nano-interfaces in relevant mechanism an increasing concentration of delocalized electrons resulting in unlocking of the Helmholtz layer capacity.

By using simple and efficient method we discuss properties of a single impurity immersed in three-dimensional Bose gas with the interaction between particles tuned to unitary limit. Particularly, adopting the mean-field-like approximation we present the first estimations for the low-momentum parameters of the impurity spectrum, namely, the binding energy, the effective mass and the quasiparticle residue both for repulsive and attractive Bose polarons in the unitary gas., 6 pages, 9 figures

The detailed mean-field treatment of the Bose polaron problem in two and three dimensions is presented. Particularly, assuming that impurity is immersed in the dilute Bose gas and interacts with bosons via the hard-sphere two-body potential, we calculate the low-momentum parameters of its spectrum, namely, the binding energy and the effective mass. The limits of applicability of the mean-field approach to a problem of mobile impurity in Bose-Einstein condensates are discussed by comparing our results to the Monte Carlo simulations data., 9 pages, 9 figures; the discussion of the 2D Bose polaron has been extended; the misleading statement about the average density of bosons has been corrected

We report on the complex GaSe-based hierarchical structures GaSe(CS(NH2)2), GaSe(SmCl3) and GaSe(CS(NH2)2(SmCl3)) synthesized by an intercalation method. The conductive properties of synthesized clathrates and their relation to hierarchical structural complexity were explored by an impedance spectroscopy technique. The impedance response, thermostimulated discharge spectra, and photo- and magnetoresistive effects are reported. Based on the obtained results, the impurity energy spectra were calculated. A strong low-frequency inductive response, observable in the GaSe(SmCl3) clathrate, makes this material promising for the development of gyrator-free nanodelay lines potentially applicable in nanoelectronics. Hierarchical GaSe(CS(NH2)2(SmCl3)) clathrate, on the other hand, reveals hysteresis of the current&ndash, voltage characteristics, apparently confirming an accumulation of electric energy at interphase boundaries. A relevant spin battery effect, observable experimentally in stationary magnetic fields, demonstrates a principal possibility of the electric energy accumulation at a quantum level.

The formula for the temperature dependence of the effective mass of a 4He atom in the superfluid and normal phases is obtained. This expression for the effective mass allows one to eliminate infra-red divergences, being applicable at all temperatures, except for a narrow fluctuation region 0.97 ≤ T/Tc ≤ 1. In the high and low temperature limits, as well as in the interactionless limit, the obtained expression reproduces the well known results. The temperature dependence of the heat capacity and the phase transition temperature Tc ≈ 2.18 K are calculated, by using the formula obtained for the effective mass. In the framework of the approach proposed in this work, the small critical index n is determined in the random phase approximation. The obtained value corresponds to the well known result., Знайдено вираз для температурної залежностi ефективної маси атома 4He в надплиннiй i нормальнiй фазах, який дозволяє усунути iнфрачервонi розбiжностi i є застосовним при всiх температурах за винятком вузької флуктуацiйної областi 0,97 ≤T/Tc ≤ 1. В границi високих i низьких температур, а також в границi виключення взаємодiї, отриманий вираз дає вiдомi результати. На основi ефективної маси розраховано хiд кривої теплоємностi, а також знайдено температуру фазового переходу Tc ≈ 2,18 K. Використовуючи запропонований в роботi пiдхiд, отримано значення малого критичного iндексу n в наближеннi хаотичних фаз, яке вiдтворює вже вiдомий результат цього наближення.

We perform the comprehensive comparison of properties of the condensate and superfluid densities for the N -component three-dimensional Bose gas with the symmetric inter- and intraspecies short-range interaction between particles. In particular, based on the large- N expansion approach for many-boson systems we obtain general expression for density of the superfluid component that at very low temperatures reproduce the well-know Landau’s formula and non-trivially includes the thermal fluctuations in the finite-temperature region, and compare it to the condensate density calculated previously. The numerically evaluated temperature dependencies are in a qualitatively good agreement with the results of Monte Carlo simulations.

On the basis of the expression for the density matrix of interacting Bose particles in the coordinate representation with regard for the direct three- and four-particle correlations [I.O. Vakarchuk and O.I. Hryhorchak, J. Phys. Stud. 3, 3005 (2009)], the two-, three-, and four-particle structure factors of liquid 4He in a wide temperature interval were calculated in the approximation “one sum over the wave vector”. In the low-temperature limit, the expression obtained for the two-particle structure factor transforms into the well-known one. In the high-temperature limit, the expressions for the two-, three-, and four-particle structure factors are reduced to those for the ideal Bose gas. The results obtained can be applied to calculations of the thermodynamic functions of liquid 4He and to the determination of the temperature dependence of the first-sound velocity in a many-boson system., На основi виразу для матрицi густини взаємодiючих бозе-частинок в координатному зображеннi iз врахуванням прямих три- i чотиричастинкових кореляцiй [I.О. Вакарчук, О.I. Григорчак, Журн. фiз. досл. 3, 3005 (2009)] були розрахованi дво-, три- i чотиричастинковi структурнi фактори рiдкого 4He в наближеннi “однiєї суми за хвильовим вектором” для широкого iнтервалу температур. В границi низьких температур отриманий вираз для двочастинкового структурного фактора переходить в уже вiдомий. В границi високих температур вирази для дво-, три- i чотиричастинкових структурних факторiв редукуються до структурних факторiв iдеального бозе-газу. Результати роботи можуть бути застосованi для розрахунку термодинамiчних функцiй рiдкого 4He i знаходження температурної залежностi швидкостi першого звуку в багатобозоннiй системi.

The purpose of this work is to expand the class of electrical energy storage devices with non-conjugate functional hybridity. Cyclodextrins of β- and γ-modifications has used as a starting material for research. These materials containing intramolecular voids, which are able to accommodate guest components by molecular recognition on the "lock-key" principle. Methods of precision porometry and impedance spectroscopy has used to study the obtained carbon structures, electrochemical and magnetic measurements has performed to study the obtained carbon structures. Data of the precision porometry has indicated a bimodal porous structure of the synthesized chars. The total specific surface area of active surface of the β-cyclodextrin carbonizate was about 72 m2/g. After KOH-modification, the specific capacity for β-cyclodextrin char was 158 F/g, and in the negative potential range – 203 F/g. The last value for γ-cyclodextrin carbon was 162 F/g. The ability of β-cyclodextrin to molecular recognition of ferrocene (FC) has used and this cavitat has subjected to activation carbonation according to the same modes as β-cyclodextrin. The specific capacity of the obtained char of the β-CD complex after the KOH-modification was 110 F/g, the specific capacity of the cavitate carbon synthesized on γ-CD has dropped twice. The study of complexes host-guest inclusions β-cyclodextrin with molecular iodine has indicated a slight increase of capacity. However, their interface with 30 % aqueous electrolyte solution has shown high photosensitivity. The specific capacitance of the cavitate carbon without KOH-modification has increased four times when it was illuminated with integral and monochromatic light from LEDs of the same intensity. Magnetic studies of the synthesized carbonates have shown that they all demonstrate ferromagnetic properties. Measurement under normal conditions and in a constant magnetic field of cells of symmetric configuration on carbon-based electrodes synthesized with γ-CD and γ-CD has showed that their capacitance practically does not change, but their reactance parameters change significantly. Supercapacitors based on these carbonates can serve as sensors of a weak magnetic field at room temperature. Magnetovarionistors is a new class of devices, which are forming on such kind of supercapacitors.

We revised the large-$N$ expansion for a three-dimensional Bose system with short-range repulsion in normal phase. Particularly, for the model potential that is characterised only by the $s$-wave scattering length $a$ the full numerical calculations of the critical temperature in the $1/N$-approximation as a function of the gas parameter $an^{1/3}$ are performed. Additionally to the well-known result in the dilute limit we estimated analytically the leading-order strong-coupling behavior of the Bose-Einstein condensation transition temperature. It is shown that the critical temperature shift of the non-ideal Bose gas grows at small $an^{1/3}$, reaches some maximal value and then falls down becoming negative., 6 pages, 3 figures

We rigorously discuss the large-$N$ thermodynamics of a Bose gas with a short-range two-body potential. Considering the system as a mixture of $N$ identical components with symmetrical interaction we calculated numerically the temperature dependence of the leading-order corrections to the depletion of Bose-Einstein condensate and to the isothermal compressibility., Comment: 5 pages, 4 figures

Based on the many-boson system structure factor, which takes into account three- and four-particle direct correlations, there was found the first sound velocity temperature behaviour in liquid $^4$He in the post-RPA approximation. The expression received for the sound velocity matches with the well-known results in both low and high temperature limits. The results of this paper can be used to analyze the contributions of three- and four-particle correlations into thermodynamic and structural features of liquid $^4$He., Comment: 7 pages, 1 figure