Generalization of Luttinger’s theorem for strongly correlated electron systems

By on the analyzing the general structure of the Green function of a strongly correlated electron system, it is shown that, for the regime of strong correlations, Luttinger’s theorem should be generalized in the following way: the volume of the Fermi surface of the system of noninteracting particles is equal to that of the quasiparticles in the strongly correlated system with due regard for the spectral weight of the quasiparticles. An investigation of the t-J model and of the Hubbard model, as applied to the paramagnetic nonsuperconducting phase, shows that the generalized Luttinger theorem is valid for these models.     

Distribution of component molecules in <Emphasis Type="Italic">p</Emphasis>-dibromobenzene-<Emphasis Type="Italic">p</Emphasis>-dichlorobenzene solid solutions from raman effect data

Distribution of component molecules in the bulk of single crystals of p-dibromobenzene-p-dichlorobenzene solid solutions grown by the Bridgman method studied by Raman effect.     

Doping-dependent evolution of low-energy excitations and quantum phase transitions within an effective model for high-T<Subscript>c</Subscript> copper oxides

In this paper a mean-field theory for the spin-liquid paramagnetic non-superconducting phase of the p- and n-type high-T_c cuprates is developed. This theory applied to the effective t-t'-t′′-J^* model with the ab initio calculated parameters and with the three-site correlated hoppings. The static spin-spin and kinematic correlation functions beyond Hubbard-I approximation are calculated self-consistently. The evolution of the Fermi surface and band dispersion is obtained for the wide range of doping concentrations x. For p-type systems the three different types of behavior are found and the transitions between these types are accompanied by the changes in the Fermi surface topology. Thus a quantum phase transitions take place at x = 0.15 and at x = 0.23.Due to the different Fermi surface topology we found for n-type cuprates only one quantum critical concentration, x = 0.2. The calculated doping dependence of the nodal Fermi velocity and the effective mass are in good agreement with the experimental data.     

Passivation of a solid gallium electrode in sulfate buffer solutions: The role played by the HSO 4 - anions

The anodic behavior of solid gallium (99.9998%) in sulfate buffer solutions is studied by the chronopotentiometric method. The resistive passivating film that forms on the electrode surface undergoes a rather rapid destruction due to the interaction of hydroxy- and oxy-groups with the electrostatically injected hydrosulfate anions. Dedicated to the ninetieth anniversary of Ya.M. Kolotyrkin’s birth.     

Oxidation of copper nanopowders on heating in air

The morphology and structure of copper nanopowders produced by electrical explosion of conductors are considered. The regularities of nanopowder oxidation in air were studied during linear and isothermal heating. The characteristics of initial powders in relation to the kinetic oxidation parameters were determined and the dependence of phase composition of the products of nanopowder oxidation on the heating conditions and dispersity of initial powders was found.     

Surface characteristics of V-Ga alloys after irradiation by Ar<Superscript>+</Superscript> and N<Superscript>+</Superscript> ions

V-5Ga-6Cr and V-5Ga-0.05Ce vanadium alloys irradiated by Ar⁺ and N⁺ ions with energies of 20 keV have been investigated. Irradiation by Ar⁺ and N⁺ ions leads to strengthening of the surface layers of samples. Their thicknesses exceed the projectile ranges of these ions (16.4 and 32.8 nm, respectively) in vanadium by more than two orders of magnitude. The experimentally determined penetration depth of argon ions is less that 70 nm. The sample side irradiated by Ar⁺ ions has a predominant orientation of crystallites in the (100) and (211) planes, while the unirradiated sample has a (110) surface. The lattice parameter of the irradiated sample does not differ from that of the initial sample. Possible mechanisms by which modified deep layers are formed during ion bombardment are discussed.     

Study of low-frequency polarized spectra of a mixed para-dibromobenzene-para-bromochlorobenzene crystal

Polarization studies of low-frequency Raman spectra of a mixed (1: 1) para-dibromobenzene-para-bromochlorobenzene crystal are performed. The spectrum of the mixed crystal is similar to the spectra of its components and also exhibits a number of additional low-intensity lines. The experimental results are interpreted using calculations of mixed crystals by the methods of atom-atom potentials and of Dean. It is found that the experimental results better agree with calculations when the disordered distribution of para-bromochlorobenzene molecules over para-positions is taken into account     

Synthesis and luminescent properties of functionalized polynorbornenes with boron-containing fragments in side chains

Russian Chemical Bulletin - New norbornene monomer, viz., 5-[(bicyclo[2.2.1]hept-5-en-2-ylmethoxy)methyl]-8-[(dimesitylboryl)oxy]quinoline (1), was synthesized. The copolymers based on monomer 1...