Superconductivity Measurements of (Hg,Tl)-1223 Compound Prepared in Capsule

In this paper, investigations were carried out on the effects of simultaneous partial substitution of Tl at the Hg site on the physical properties of an Hg1-xTlxBa2Ca2Cu3O8+δ cuprate superconductor with x= 0, 0.1, 0.2, 0.3 and 0.4. Two steps of the solid state reaction method were used to prepare samples in capsule. The results showed that the optimum sintering temperature was equal to 850 ᵒC and the sintering time was equal to 20 h for the prepared samples. The best conditions for constitution and stabilization of the high Tc phase-1223 were obtained by investigating the effects of Tl substitution on Hg site and oxygen content (δ) on the superconducting properties. Structural investigation revealed that all the samples have a tetragonal structure with two phases, namely an Hg-1223 high Tc phase as a main phase and an Hg-1212 low Tc phase. Besides, some impurity phases like CuO and CaHgO2 were found. The increase of Tl content in Hg1-xTlxBa2Ca2Cu3O8+δ compound from 0 to 0.4 caused a change in the lattice parameter, density of the unit cell (ρm), and c/a values. HgBa2Ca2Cu3O8+δ compound exhibited a critical transition temperature that is equal to 115 K. On the other side, the results showed that the highest Tc was 119 K for Hg0.8Tl0.2 Ba2Ca2Cu3O8+δ. The oxygen content (δ= 0.46) was expected to be the optimum hole doping for Hg0.8Tl0.2 Ba2Ca2Cu3O8+δ compound, which means in our opinion that δ plays a remarkable role in the assessment of Tc.

Comparison of estimation methods for the density of autoregressive parameter in aggregated AR(1) processes

The article investigates the properties of two alternative disaggregation methods. First one, proposed in Chong (2006), is based on the assumption of polynomial autoregressive parameter density. Second one, proposed in Leipus et al. (2006), uses the approximation of the density by the means of Gegenbauer polynomials. Examining results of Monte-Carlo simulations it is shown that none of the methods was found to outperform another. Chong’s method is narrowed by the class of polynomial densities, and the secondmethod is not effective in the presence of common innovations.Bothmethodswork correctly under assumptions proposed in the corresponding articles.

Distinguishing noisy boson sampling from classical simulations

Giving a convincing experimental evidence of the quantum supremacy over classical simulations is a challenging goal. Noise is considered to be the main problem in such a demonstration, hence it is urgent to understand the effect of noise. Recently found classical algorithms can efficiently approximate, to any small error, the output of boson sampling with finite-amplitude noise. In this work it is shown analytically and confirmed by numerical simulations that one can efficiently distinguish the output distribution of such a noisy boson sampling from the approximations accounting for low-order quantum multiboson interferences, what includes the mentioned classical algorithms. The number of samples required to tell apart the quantum and classical output distributions is strongly affected by the previously unexplored parameter: density of bosons, i.e., the ratio of total number of interfering bosons to number of input ports of interferometer. Such critical dependence is strikingly reminiscent of the quantum-to-classical transition in systems of identical particles, which sets in when the system size scales up while density of particles vanishes.

Is the relation between the solar wind dynamic pressure and the magnetopause standoff distance so simple?

<p>The relation between the solar wind dynamic pressure and magnetopause standoff distance is usually supposed to be R<sub>SUB</sub>~P<sub>d</sub><sup>-1/N</sup>. The simple pressure balance condition gives N=6, however N varies in empirical magnetopause models from 4.8 to 7.7. Using several MHD models, we simulate the magnetospheric response to increases in the dynamic pressure by varying separately the solar wind density or the velocity. We obtain different values of N depending on which parameter, density or velocity, has been varied and for which IMF orientation. The changes in the standoff distance are smaller (higher N) for a density increase and greater (smaller N) for a velocity increase for southward IMF. We explain this result by enhancement of the Region 1 current that moves the magnetopause closer to the Earth for a high solar wind velocity. We suggest for developers of new empirical magnetopause models in the future to replace the simple relation between R<sub>SUB</sub> and P<sub>d</sub> with a fixed N by a more complicated relation which would separate inputs in the dynamic pressure from the density and velocity taking into account the IMF orientation.</p>

Impurity-induced tunneling-mediated superconducting gap in bilayer cuprate superconductors

We have proposed a model Hamiltonian describing the interlayer tunneling in d-wave bilayer cuprate superconductors. The Hamiltonian is solved for the quasi-particle energy bands and the superconducting (SC) order parameter by using Zubarev’s technique of double time Green’s functions. The effects of interlayer tunneling and the strength of non-magnetic potential are studied for SC order parameter, density of states (DOS), electronic specific heat and quasi-particle energy bands, and the results are compared with others.