Large non-adiabatic hole polarons and matrix element effects in the angle-resolved photoemission spectroscopy of dielectric cuprates

It has been made an extention of the conventional theory based on the assumption of the well isolated Zhang-Rice singlet to be a first electron-removal state in dielectric copper oxide. One assumes the photohole has been localised on either small (pseudo)Jahn-Teller polaron or large non-adiabatic polaron enclosed one or four to five $CuO_4$ centers, respectively, with active one-center valent $(^{1}A_{1g}-{}^{1,3}E_{u})$ manifold. In the framework of the cluster model we have performed a model microscopic calculation of the ${\bf k}$-dependence of the matrix element effects and photon polarization effects for the angle-resolved photoemission in dielectric cuprate like $Sr_{2}CuO_{2}Cl_{2}$. We show that effects like the ''remnant Fermi surface'' detected in ARPES experiment for $Ca_{2}CuO_{2}Cl_{2}$ may be, in fact, a reflection of the matrix element effects, not a reflection of the original band-structure Fermi surface, or the strong antiferromagnetic correlations. The measured dispersion-like features in the low-energy part of the ARPES spectra may be a manifestation of the complex momentum-dependent spectral line-shape of the large PJT polaron response, not the dispersion of the well-isolated Zhang-Rice singlet in antiferromagnetic matrix.Comment: 16 pages, TeX, 9 eps figures adde

Mass distributions for nuclear disintegration from fission to evaporation

By a proper choice of the excitation energy per nucleon we analyze the mass distributions of the nuclear fragmentation at various excitation energies. Starting from low energies (between 0.1 and 1 MeV/nucleon) up to higher energies about 12 MeV/n, we classified the mass yield characteristics for heavy nuclei (A>200) on the basis of Statistical Multifragmentation Model. The evaluation of fragment distribution with the excitation energy show that the present results exhibit the same trend as the experimental ones.Comment: 5 pages, 3 figure

Phase equilibria and thermodynamic properties of oxide systems on the basis of rare earth, alkaline earth and 3d-transition (Mn, Fe, Co) metals. A short overview of

Review is dedicated studies of phase equilibria in the systems based on rare earth elements and 3d transition metals. It’s highlighted several structural families of these compounds and is shown that many were found interesting properties for practical application, such as high conductivity up to the superconducting state, magnetic properties, catalytic activity of the processes of afterburning of exhaust gases, the high mobility in the oxygen sublattice and more

Development of an automated prototype of THz filter based on magnetic fluids

Many new investigation approaches or techniques that rely on THz radiation are emerging today. It requires the development of devices for controlling THz radiation characteristics intensity, polarization, spectral properties, etc. One of the promising approaches to the implementation of such devices is the use of ferromagnetic fluids. Earlier, the efficient operation of polarizers and non selective THz attenuators based on ferromagnetic liquids was demonstrated. The liquids used consisted of 5BDSR alloy particles obtained by the mechanical synthesis in a planetary mill or Fe particles obtained by the electric explosion, dispersed in synthetic engine oil. Magnetic fluids were controlled using an external magnetic field generated by Helmholtz coils. In this study, we propose a prototype of a THz filter based on previously developed ferromagnetic fluids. Filter consists of a quartz or polymer cuvette with a magnetic fluid, several Helmholtz coils and a control circuit. This device allows one to orient the magnetic particles and to create ordered structures in the form of extended clusters. As a result, physical properties of electromagnets were optimized for effective controlling of particle clusters; the control process itself was automated. Spectral properties in the THz range are studied for various filter states. For reliable continuous operations, the device was supplemented with a homogenization system, based on mechanical mixing or sonication. The developed device can be used as a polarizer or an attenuator for polarized radiation in the range of 0.3-3 THz

Parametric Generation of Second Sound by First Sound in Superfluid Helium

We report the first experimental observation of parametric generation of second sound (SS) by first sound (FS) in superfluid helium in a narrow temperature range in the vicinity of $T_\lambda$. The temperature dependence of the threshold FS amplitude is found to be in a good quantitative agreement with the theory suggested long time ago and corrected for a finite geometry. Strong amplitude fluctuations and two types of the SS spectra are observed above the bifurcation. The latter effect is quantitatively explained by the discreteness of the wave vector space and the strong temperature dependence of the SS dissipation length.Comment: 4 pages, 4 postscript figures, REVTE

Results of applying acidic hydraulic fracturing with proppant in the Tournaisian-Famennian reserves at the Ozernoe field

The paper is devoted to the efficiency of acidic hydraulic fracturing – the most widespread method of well stimulation for the Tournaisian-Famennian carbonate reserves found in the Ozernoe field. All the operations performed may be divided in two groups: acidic hydraulic fracturing performed by the conventional technology when fracture openness is reached by wall profile following the reaction of acid with rock, and acidic hydraulic fracturing with proppant. At the site investigated 12 operations of proppant fracturing were performed. To assess the results, including comparison with the conventional acidic hydraulic fracturing, the well investigation data were obtained under nonsteady flow before and after the treatment. In doing so, pressure build up curves were processed by standard methods and that of Warren-Root to evaluate fracturing level. Two wells were chosen with similar production profile and formation flow characteristics prior to well intervention, which were explored twice afterwards. The reservoir was classified as porous for both wells in accordance with pressure build up curve. Following acidic hydraulic fracturing in both cases reservoir fracturing was observed with average fracture openness from 10 to 30 µm. However, nine months after the intervention no fracture were found in the well subjected to conventional acidic hydraulic fracturing, with the same formation flow and production characteristics as before the intervention. The well processed by proppant acidic hydraulic fracturing demonstrates fracturing immediately after the intervention and almost two years later, which testifies to the technology efficiency. The conclusions made were confirmed by field data

Development of the methodology for evaluation of possibilities to determine reservoir types based on pressure build-up curves, geological and reservoir properties of the formation (case study of famen deposits of Ozernoe field)

One of the features of geological structure of Famen deposits of Ozernoe field is naturally fractured reservoir zones. Results of hydrodynamic study of wells on unsteady regime that were processed by Warren-Root model show that naturally fractured zones are oriented North-East. In order to prove existence of zones with different reservoirs statistical analysis was performed. Wherein geological and physical reservoir parameters (absolute elevation, thickness, permeability), several parameters of well performance (initial rate, productivity index) and litho-facial analysis (on cores and seismic) were additionally involved. In this paper interval probabilities that belong to naturally fractured and pore types are determined. Average values of varying intervals compared with interval probabilities. Based on that data pair correlation coefficients calculated and regression equations are built taking into account all studying parameters. Correlation between probability values and addition values are shown on graph. Graphs show probability of naturally fractured reservoir existence for different values of geological and technological parameters. To build the optimal forecast model using individual probability generalized probability were calculated. Scheme that reflect its change on the area of the deposit is built. Analysis show that wells belong to cavitation type determined base on pressure build-up curves in accordance with Warren-Root model is proved by obtained reservoir characteristics. The methodology for reservoir type determination has several advantages, can be implemented on the other fields that are similar in terms of geological structure and Oil and Gas province

Large Non-Adiabatic Hole Polarons and Matrix Element Effects in the Angle-Resolved Photoemission Spectroscopy of Dielectric Cuprates

We propose a generalization of the conventional theory based on the assumption of the well-isolated Zhang-Rice 1A1g singlet to be a first electron-removal state in insulating copper oxide. The photohole is assumed to be localized on either small (pseudo) Jahn-Teller (PJT) polaron or large non-adiabatic polaron-enclosed one or four to five CuO4 centers, respectively, with active one-center valent (1A1g-1,3Eu) manifold. In the framework of the cluster model we have performed the model microscopic calculation of the k-dependence of the matrix element effects and photon polarization effects for the angle-resolved photoemission (ARPES) in insulating cuprates like Sr2CuO2Cl2. We show that effects like the "remnant Fermi surface" detected in the ARPES experiment for Ca2CuO2Cl2 may be, in fact, the manifestation of the matrix element effects rather than of the original band-structure Fermi surface or strong antiferromagnetic correlations. The measured dispersion-like features in the low-energy part of the ARPES spectra may be the manifestation of the complex momentum-dependent spectral line shape of the large PJT polaron response, in addition to the dispersion effect for the well-isolated Zhang-Rice singlet in antiferro-magnetic matrix. © 2002 Elsevier Science B.V. All rights reserved.We wish to thank S.-L. Drechsler and R. Hayn for valuable discussions. The research described in this publication was made possible in part by Award No. REC-005 of the US Civilian Research & Development Foundation for the Independent States of the Former Soviet Union (CRDF). The authors acknowledge a partial support from the Russian Ministry of Education, Grant E00-3.4-280, and Russian Foundation for Basic Researches, Grant 01-02-96404

The influence of the dislocation distribution heterogeneity degree on the formation of a non-misoriented dislocation cell substructures in f.c.c. metals

Dislocation loops emitted by Frank-Reed source during crossing dislocations of the non-coplanar slip systems are accumulates jogs on the own dislocation line, resulting in the deceleration of the segments of dislocation loops with high jog density. As a result, bending around of the slowed segments the formation of dynamic dipoles in the shear zone occurs. In the present paper we consider formation mechanism of non-misoriented dislocation cell substructure during plastic deformation of f.c.c. metals and conclude that the increase in the degree heterogeneity of dislocation distribution leads to an increase in the jog density and reduce the mean value of arm dynamic dipoles