The ${\mathrm{TlBaCa}}_{3}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{8.5}$ superconductor contains two main superconducting phases, 1:2:2:3 and 2:2:2:3, identified by powder x-ray analysis. Using $^{57}\mathrm{Fe}$ M\"ossbauer nuclei as the probe, it has been confirmed that the results are the same as those furnished by x-ray analysis. It has also been proved that iron atoms in the lattice substitute two inequivalent sites of copper atoms for each main phase. We have observed a temperature dependence of the M\"ossbauer parameters, i.e., quadrupole splitting, isomer shift, and relative resonance area. Here several problems are discussed related to the lattice dynamics and the electric charge transfer, which takes place in the transition from normal state to superconducting state.

Mössbauer observation near the superconducting transition temperature in the TlBaCa3Cu3O8.5 superconductor.

Pb-doped Tl-Ba-Ca-Cu-O compounds with nominal composition TlPb{sub {ital x}}BaCa{sub 3}Cu{sub 3}O{sub {ital y}} have been sintered, and their physical properties have been studied. It is found that the superconducting transition temperature of the samples drops with the increase of {ital x}. The crystal structure is tetragonal, and the lattice constants reduce with Pb content. Precipitated phases are also present in the Pb-doped samples. The pressure dependence of {ital T}{sub {ital c}} for the Pb-doped samples has also been studied. It is found that {ital T}{sub {ital c}} increases with pressure at a rate of {ital dT}{sub {ital c}}{sup {ital R}=0}/dP=0.22 K/kbar for {ital x}=0.5, a higher rate than the {ital dT}{sub {ital c}}{sup {ital R}=0}/dP=0.18 K/kbar for pure Tl-Ba-Ca-Cu-O.

Superconductivity and its pressure dependence in the Pb-doped Tl-Ba-Ca-Cu-O superconductors

We discuss the generalized parton distributions (GPDs) for unpolarized hadrons, as a continuation of our recent work on hadronic structure on the light front. We analyze the unpolarized GPDs for the light nucleon and delta, as well as generic mesons, using the lowest Fock states. We use these GPDs to reconstruct the charge and gravitational form factors, and discuss their relative sizes. The results are also compared to reported QCD lattice results. 

/pdf/hadronic-structure-on-the-light-front-vi-generalized-parton-20xzdtck.pdf

Hadronic structure on the light-front. VI. Generalized parton distributions of unpolarized hadrons

Femtoscopy of the Matter Distribution in the Proton

In order to study how Mn substitution changes the superconducting properties of the TlBaCaCuO compound, we have prepared samples with Mn in place of Cu, Tl and Ca respectively by solid-state reactions. We have examined their superconductive transitions by measurements of their resistive and magnetic behaviors, which show that Mn has a negative effect on the superconductivity. It has been found by energy dispersive spectrometry (EDS) and by secondary-ion mass spectrometry (SIMS) that even a relatively small amount of Mn can cause a significant loss of Cu and Tl in the Tl compound. X-ray diffraction and morphological analysis have shown that Mn can also bring in precipitated phases of BaCuO 2 and MnO 2 .

Influence of Mn on the superconductivity of the TlBaCaCuO system

The proton is one of the main building blocks of all visible matter in the Universe1. Among its intrinsic properties are its electric charge, mass and spin2. These properties emerge from the complex dynamics of its fundamental constituents—quarks and gluons—described by the theory of quantum chromodynamics3–5. The electric charge and spin of protons, which are shared among the quarks, have been investigated previously using electron scattering2. An example is the highly precise measurement of the electric charge radius of the proton6. By contrast, little is known about the inner mass density of the proton, which is dominated by the energy carried by gluons. Gluons are hard to access using electron scattering because they do not carry an electromagnetic charge. Here we investigated the gravitational density of gluons using a small colour dipole, through the threshold photoproduction of the J/ψ particle. We determined the gluonic gravitational form factors of the proton7,8 from our measurement. We used a variety of models9–11 and determined, in all cases, a mass radius that is notably smaller than the electric charge radius. In some, but not all cases, depending on the model, the determined radius agrees well with first-principle predictions from lattice quantum chromodynamics12. This work paves the way for a deeper understanding of the salient role of gluons in providing gravitational mass to visible matter. The gluonic gravitational form factor of the proton was determined using various models, and these analyses showed that the mass radius of the proton was smaller than the electric charge radius. 

Determining the gluonic gravitational form factors of the proton

We synthesized new superconducting phases in TlBa2Can-1CunO2n+2.5 by solid state reaction. The crystal structures of TlBa2CaCu2O6.5 and TlBa2Ca2Cu3O8.5 were determined by means of X-ray powder diffraction method. The two compounds belong to primary lattice with space group D4h1-P4/mmm. The lattice constants of TlBa2CaCu2O6.5 areα= 3.847 A, c = 12.73 A. The lattice constants of TlBa2Ca2Cu3O8.5 are a = 3.847A, c= 15.89A. Each cell contains one chemical formula unit. The cations are distributed alternately at positions of (0,0,z) and (1/2, 1/2, z) along Z axis.
TlBa2CaCu2O6.5 shows zero resistance at 101.4K. TlBa2Ca2Cu3O8.5 shows zero resistance at 112K. The oxygen deficient pseudo-perovskite unit Ba2Can-1CunO2n+1 is separated by single Tl-O layer in the crystal structure of TlBa2Can-1CunO2n+2.5, while the oxygen deficient pseudo-perovskite unit Ba2Can-1CunO2n is separated by bilayer of Tl-O in the crystal structure of Tl2Ba2Can-1CunO2n+2· At the same n value, Tc of Tl2Ba2Can-1CunO2n+4 is about 10K higher than Tc of TlBa2Can-1CunO2n+2.5· This indicates that Tc depends on the number of Tl-O layer as well as the number of [CuO5] and [CuO4] in oxygen deficient pseudo-perovskite unit Ba2Can-1Cun O2n.

The crystal-structures and superconductivity of a new series of superconducting phases

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Determining the gluonic gravitational form factors of the proton

The crystal-structures and superconductivity of a new series of superconducting phases