The electronic pseudogap in optimally doped NCCO

We study the effect of antiferromagnetic correlations in the three-band Emery model, in comparison with the experimental angle-resolved photoemission (ARPES) spectra in optimally doped NCCO. The same calculation, formerly used to describe BSCCO, is relevant here, but in contrast to BSCCO, where quantum paramagnon fluctuations are important, the characteristic energy of the dispersive paramagnons in NCCO is of the order of Tc. The wide dispersing features of the single-electron spectrum in NCCO are analogous to the BSCCO hump. The Fermi surface is pseudogapped in both the nodal and antinodal directions, although the detailed features differ, being dominated by loss of intensity in the nodal direction, and loss of coherence in the antinodal one. Direct oxygen-oxygen hopping is important in NCCO as well as in BSCCO, in order to obtain overall agreement with the measured ARPES spectra.Comment: Final version as accepted in PRB(RC), one paragraph added, 4 pages, 3 figure

Resistivity phase diagram of cuprates revisited

The phase diagram of the cuprate superconductors has posed a formidable scientific challenge for more than three decades. This challenge is perhaps best exemplified by the need to understand the normal-state charge transport as the system evolves from Mott insulator to Fermi-liquid metal with doping. Here we report a detailed analysis of the temperature (T) and doping (p) dependence of the planar resistivity of simple-tetragonal HgBa$_2$CuO$_{4+\delta}$ (Hg1201), the single-CuO$_2$-layer cuprate with the highest optimal $T_c$. The data allow us to test a recently proposed phenomenological model for the cuprate phase diagram that combines a universal transport scattering rate with spatially inhomogeneous (de)localization of the Mott-localized hole. We find that the model provides an excellent description of the data. We then extend this analysis to prior transport results for several other cuprates, including the Hall number in the overdoped part of the phase diagram, and find little compound-to-compound variation in (de)localization gap scale. The results point to a robust, universal structural origin of the inherent gap inhomogeneity that is unrelated to doping-related disorder. They are inconsistent with the notion that much of the phase diagram is controlled by a quantum critical point, and instead indicate that the unusual electronic properties exhibited by the cuprates are fundamentally related to strong nonlinearities associated with subtle nanoscale inhomogeneity.Comment: 22 pages, 5 figure

Identification and Quantification of Raw Materials During Designing of Cast Producing Process

It is investigated the possibility to be accounted the raw material’s quantity for each casting on the basis of design draft and mass of casting. To precisely determine the quantity of raw materials is necessary to technological procedure is preliminary accomplished. This task can be reached if correlations between kind of castings, shape complexity of castings, relations between total and net mass of castings, relations between mass of cores and mass of net casting will be established, with all respect toward applied technology and production methods of cores, the molding box and models

Mikrovalna vodljivost tankih listova YBCO u magnetskom polju

The microwave response of a thin film of high temperature superconductor YBa2Cu3O7 - δ was measured for a wide region of temperatures and magnetic fields. From the measured complex frequency shift, the complex conductivity was calculated. The model for effective conductivity in the mixed state was fitted to the complex conductivity data and the values of upper critical fields Bc2(T) and depinning frequencies ω0 (T) have been obtained as fitted parameters.Mjerili smo mikrovalni odziv tankog filma visokotemperaturnog supravodiča YBa2Cu3O7−δ u širokom području temperatura i magnetskih polja. Iz izmjerenog kompleksnog frekventnog pomaka izračunali smo kompleksnu vodljivost. Numeričkom prilagodbom modela efektivne vodljivosti u miješanom stanju odredili smo vrijednosti gornjeg kritičnog polja Bc2 (T) i frekvencije opuštanja ω0(T)

Diagrammatic content of the DMFT for the Holstein polaron problem in finite dimensions

In the context of the Holstein polaron problem it is shown that the dynamical mean field theory (DMFT) corresponds to the summation of a special class of local diagrams in the skeleton expansion of the self-energy. In the real space representation, these local diagrams are characterized by the absence of vertex corrections involving phonons at different lattice sites. Such corrections vanish in the limit of infinite dimensions, for which the DMFT provides the exact solution of the Holstein polaron problem. However, for finite dimensional systems the accuracy of the DMFT is limited. In particular, it cannot describe correctly the adiabatic spreading of the polaron over multiple lattice sites. Arguments are given that the DMFT limitations on vertex corrections found for the Holstein polaron problem persist for finite electron densities and arbitrary phonon dispersion.Comment: 5 pages, 3 figure