Structural behavior of Pby_yBi1.95−y_{1.95-y}Sr1.49_{1.49}La0.4_{0.4}Cu1.15_{1.15}O6+δ_{6+\delta} for 0<y<0.53

In the Bi cuprates, the presence of a near 1$\times$5 superstructure is well known. Usually, this superstructure is suppressed by the substitution of lead, but there have been reports of a phase separation in so called {\alpha} and {\beta} phases. This paper shows in high detail time how and why the phase separation develops and what happens to the quasi-1$\times$5 superstructure upon lead substitution. For this purpose, the lanthanum- and lead-substituted single-layered superconductor Bi$_{2+z}$Sr$_{2-z}$CuO$_{6+\delta}$ has been investigated by scanning tunneling microscopy and low-energy electron diffraction. The La content was kept constant at slightly under-doped concentration while the Pb content was changed systematically. Thermodynamic considerations show that a phase mixture of {\alpha} and {\beta} phases is inevitable.Comment: 17 pages, 4 figure

Atualidades e desafios nas fases de crescimento e terminação: 1) sistemas de alimentação.

Projeto: 11.11.11.111

Novos desenvolvimentos na nutrição dos leitões nas fases de crescimento e terminação.

Projeto/Plano de Ação: 03.07.05.019

Uso de permeado spray-dried (PERLAC 850®) produzido a partir de soro de leite doce em substituição ao soro de leite e à lactose pura em dietas de leitões recém-desmamados.

bitstream/item/78977/1/Comunicado-507.pdfProjeto/Plano de Ação: 03.12.01.025

Spectroscopic signatures of a bandwidth-controlled Mott transition at the surface of 1T-TaSe2_2

High-resolution angle-resolved photoemission (ARPES) data show that a metal-insulator Mott transition occurs at the surface of the quasi-two dimensional compound TaSe$_2$. The transition is driven by the narrowing of the Ta $5d$ band induced by a temperature-dependent modulation of the atomic positions. A dynamical mean-field theory calculation of the spectral function of the half-filled Hubbard model captures the main qualitative feature of the data, namely the rapid transfer of spectral weight from the observed quasiparticle peak at the Fermi surface to the Hubbard bands, as the correlation gap opens up.Comment: 4 pages, 4 figures; one modified figure, added referenc

Luttinger liquid phenomenology and angle resolved photoemission for single layer \chem{Bi_2Sr_{2-x}La_xCuO_{6+\delta}} high--temperature superconductor

Recently observed splitting in angular resolved photoemission spectroscopy (ARPES) on \chem{Bi_2Sr_{2-x}La_xCuO_{6+\delta}} high--temperature superconductor (Janowitz C. {\it et al.}, {\it Europhys. Lett.}, {\bf 60} (2002) 615) is interpreted within the phenomenological Luttinger--liquid framework, in which both the non--Fermi liquid scaling exponent of the spectral function and the spin--charge separation are introduced. The anomalous Green function with adjustable parameters fits very well to the Fermi edge and the low--energy part of ARPES along the $\Gamma-M$ line in the Brillouin zone. In contrast to one--dimensional models with Luttinger--liquid behavior we find that both the anomalous scaling $\alpha$ and the parameter $\delta$ describing the spin--charge separation are momentum dependent. The higher--energy part of the spectra is not accounted for by this simple Luttinger--liquid form of the Green function. In this energy regime additional scattering processes are plausible to produce the experimentally observed wide incoherent background, which diminishes as the inverse of the energy.Comment: 7 pages, 3 figures, EPL styl

Suplementação de alimento lácteo líquido para leitões recém-nascidos.

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