Thermodynamics of symmetric spin--orbital model: One- and two-dimensional cases

The specific heat and susceptibilities for the two- and one-dimensional spin--orbital models are calculated in the framework of a spherically symmetric self-consistent approach at different temperatures and relations between the parameters of the system. It is shown that even in the absence of the long-range spin and orbital order, the system exhibits the features in the behavior of thermodynamic characteristics, which are typical of those manifesting themselves at phase transitions. Such features are attributed to the quantum entanglement of the coupled spin and orbital degrees of freedom.Comment: 7 pages, 9 figures, submitted to JETP Letter

Electrical resistivity, hall coefficient, and thermopower of optimally doped high-T c superconductors

© 2014, Pleiades Publishing, Inc. For a two-dimensional optimally doped antiferromagnet with spin S =1/2, we study the temperature dependence of the electrical resistivity ρ(T), Hall coefficient RH(T), and thermopower Q(T). The temperature dependence corresponding to optimally doped layered high-Tc superconducting cuprates has been obtained simultaneously for all three transport coefficients within the unified spin-polaron approach for the Kondo lattice. The key features of our study are the usage of the multimoment method for solving the kinetic equations (seven moments for the nonequilibrium distribution function ensure a good convergence) and the form of ac spin susceptibility χ(q, ω) for localized spins. For χ(q, ω), we choose a self-consistent expression which takes into account the “crossover” between the spin susceptibility determined by the self-consistent spherically symmetric Green’s function method and the semiphenomenological spin susceptibility corresponding to the critical decay of magnons

Many-Body Approch to Spin-Dependent Transport in Quantum Dot Systems

By means of a diagram technique for Hubbard operators we show the existence of a spin-dependent renormalization of the localized levels in an interacting region, e.g. quantum dot, modeled by the Anderson Hamiltonian with two conduction bands. It is shown that the renormalization of the levels with a given spin direction is due to kinematic interactions with the conduction sub-bands of the opposite spin. The consequence of this dressing of the localized levels is a drastically decreased tunneling current for ferromagnetically ordered leads compared to that of paramagnetically ordered leads. Furthermore, the studied system shows a spin-dependent resonant tunneling behaviour for ferromagnetically ordered leads.Comment: 8 pages, 5 figure

Referees Court as an Alternative Way of Settlement of Disputes in the Sphere of Business: History and Present

In the article, problems of activity of the referees courts on the example of Ancient Rome and its current state are considered. For our country the referees courts — rather new system of solving of economic disputes. Now activity of the referees courts is subject to criticism from business community and demands further improvement. One of the main advantages of transfer to the referees court of the arisen dispute is its faster consideration. Nevertheless, now the number of appeals to the referees courts are not enough. The low authority of institute of the referees courts and low awareness of citizens on advantages of referees trial is the main reason of this circumstance. Transformation of the referees court into full-fledged institute of protection of the rights and legitimate interests of representatives of a business community is a priority task for society and the state

Historical and Legal Aspect of Consideration by the Courts of the Pskov Region of Citizens’ Complaints in the Economic Sphere at the Final Stage of the History of the Soviet State

The purpose of this article is to study the process of development and functioning of the judicial institutions of the Pskov region at one of the turning points in the history of our country on the eve of the collapse of the Soviet Union and the formation of a sovereign Russian state. In the context of the socio-political and economic reforms of the Perestroika period, the judicial system did not remain aloof from the new trends in state policy. The content and main directions of the implementation of judicial policy in the field of civil rights are changing. Radical changes in the life of the country were reflected in the activities of the judicial authorities of the Pskov region regarding the work with citizens’ complaints on economic issues

Performances and stability of a 2.4 ton Gd organic liquid scintillator target for antineutrino detection

In this work we report the performances and the chemical and physical properties of a (2 x 1.2) ton organic liquid scintillator target doped with Gd up to ~0.1%, and the results of a 2 year long stability survey. In particular we have monitored the amount of both Gd and primary fluor actually in solution, the optical and fluorescent properties of the Gd-doped liquid scintillator (GdLS) and its performances as a neutron detector, namely neutron capture efficiency and average capture time. The experimental survey is ongoing, the target being continuously monitored. After two years from the doping time the performances of the Gd-doped liquid scintillator do not show any hint of degradation and instability; this conclusion comes both from the laboratory measurements and from the "in-tank" measurements. This is the largest stable Gd-doped organic liquid scintillator target ever produced and continuously operated for a long period

Dispersion of the dielectric function of a charge-transfer insulator

We study the problem of dielectric response in the strong coupling regime of a charge transfer insulator. The frequency and wave number dependence of the dielectric function $\epsilon ({\bf q},\omega)$ and its inverse $\epsilon ^{-1}({\bf q},\omega)$ is the main object of consideration. We show that the problem, in general, cannot be reduced to a calculation within the Hubbard model, which takes into account only a restricted number of electronic states near the Fermi energy. The contribution of the rest of the system to the longitudinal response (i.e. to $\epsilon ^{-1}({\bf q},\omega)$) is essential for the whole frequency range. With the use of the spectral representation of the two-particle Green's function we show that the problem may be divided into two parts: into the contributions of the weakly correlated and the Hubbard subsystems. For the latter we propose an approach that starts from the correlated paramagnetic ground state with strong antiferromagnetic fluctuations. We obtain a set of coupled equations of motion for the two-particle Green's function that may be solved by means of the projection technique. The solution is expressed by a two particle basis that includes the excitonic states with electron and hole separated at various distances. We apply our method to the multiband Hubbard (Emery) model that describes layered cuprates. We show that strongly dispersive branches exist in the excitonic spectrum of the 'minimal' Emery model ($1/U_d=U_p=t_{pp}=0$) and consider the dependence of the spectrum on finite oxygen hopping $t_{pp}$ and on-site repulsion $U_p$. The relationship of our calculations to electron energy loss spectroscopy is discussed.Comment: 22 pages, 5 figure