Impact of Heat Treatments and Hole Density (p) on the Structural, Electrical, and Superconducting Properties of LnSrBaCu3O6+z (Ln = Eu, Sm, Nd) Compounds

In this study, we thoroughly examined the impact of heat treatments and hole count (p) on the properties of LnSrBaCu3O6+z (Ln = Eu, Sm, Nd) compounds. We focused on preparation, X-ray diffraction with Rietveld refinement, AC susceptibility, DC resistivity measurements, and heat treatment effects. Two heat treatment types were applied: oxygen annealing [O] and argon annealing followed by oxygen annealing [AO]. As the rare earth Ln’s ionic radius increased, certain parameters notably changed. Specifically, c parameter, surface area S, and volume V increased, while critical temperature Tc and holes (p) in the CuO2 plane decreased. The evolution of these parameters with rare earth Ln’s ionic radius in [AO] heat treatment is linear. Regardless of the treatment, the structure is orthorhombic for Ln = Eu, tetragonal for Ln = Nd, orthorhombic for Ln = Sm [AO], and pseudo-tetragonal for Sm [O]. The highest critical temperature is reached with Ln = Eu (Tc [AO] = 87.1 K). Notably, for each sample, Tc [AO] surpasses Tc [O]. Observed data stems from factors including rare earth ionic size, improved cationic and oxygen chain order, holes count p in Cu(2)O2 planes, and in-phase purity of [AO] samples. Our research strives to clearly demonstrate that the density of holes (p) within the copper plane stands as a determinant impacting the structural, electrical, and superconducting properties of these samples. Meanwhile, the other aforementioned parameters contribute to shaping this density (p).

Thin bed responses and correction methods for cased hole density logging

The study of the thin bed responses and correction methods in cased hole density logging can provide a theoretical basis for research to improve data processing methods. By using the Monte Carlo program MCNP, the change of detector count from thin beds with the vertical depth was calculated at different casing thicknesses. The calculation showed that with the low density thin bed moving upward, detector count first increased to a maximum then decreased. The responses of a thin bed with a high density were opposite to those of a thin bed with a low density. The change curve was symmetrical, and the maximums or minimums appeared at the midpoint between the detector and source. Besides, detector count increased with increasing thin bed thickness. At a specific thin bed thickness, further increase of thin bed thickness resulted in a slow increase of detector count then the count rate leveled off. In actual logging, the influence of adjacent formations on density log measurements can be ignored. Finally, based on numerical simulation correction methods for the dual influence of casing and thin beds are discussed.

2D Modeling of Solar Cell Radial Junction: Study of Carriers Charge Density and Photocurrent Density in Static Mode under Monochromatic Illumination

A theoretical study of a polysilicon solar cell with a radial junction in static regime under monochromatic illumination is presented in this paper. The junction radial solar cell geometry is illustrated and described. The carriers’ diffusion equation is established and solved under quasi-neutral base assumption with boundaries conditions and Bessel equations. New analytical expressions of electrons and holes density and photocurrent are found. The wavelength and structural parameters (base radius, emitter thickness) influences on charge carriers density and photocurrent are shown and examined.

The Influence of Electron Transfer on Tc in Superconductors

Increase of Tc in Al1−x(SiO2)x cermets with increasing x is caused by electron transfer from the Al grains to the SiO2 phase occupying surface states, expressed by Tc/Tc,max=1−γ⋅n2(*), where n is the electron density in the Al phase and γa characteristic parameter. Decrease of Tc in Pb-Cu-sandwiches is attributed to the electron transfer from the Cu film to the Pb film. γand Tc,maxin equation (*) stands for the influence of the electron-phonon interaction and n2for the influence of the electron-electron Coulomb repulsion on Tc. The result that equation (*) holds for both hole-doped cuprate high-temperature superconductivity (HTSC) and Al1−x(SiO2)x cermets is an important indication that common mechanisms underlie HTSC and classical superconductors. The difference between the two is that in HTSC, electron transfer occurs between different electronic bands, but in Al1−x(SiO2)x cermets between different phases.

High-Temperature Superconductivity—An Electron Transfer Phenomenon

The increase of the critical temperature Tc for superconductivity in Al1−x(SiO2)x cermets with increasing x correlates with a decrease of the electron density n due to electron transfer, expressed by Tc/Tc,max=1−γ⋅n2(*). Behind the formula (*) and Tc/Tc,max=1−82.6(P−0.16)2, which is characteristic of hole-doped cuprat high-temperature superconductors, lies a general phenomenon, namely electron transfer, which equalizes potential differences in the material and leads to a strong reduction of n. P is the fraction of holes filled by the transferred electrons. A quantitative consideration gives Tc(x)/Tc,max=1−(1−x1−x0)2(**), where x is the doping concentration and x0 is the concentration at which superconductivity begins. At x=xmax=1the electron source is completely depleted and with further growth of x the hole density p starts to increase and Tc decreases until superconductivity disappears completely at x=2−x0. Taking into account the formula (**), the hypothesis arose that for x>xmaxTc/Tc,max=1−γ⋅p2(***), an analogue of the formula (*), and that superconductivity is possible not only by electron-Cooper pairs but also by paired holes. The mechanisms described here for HTSC suggest an analogy to the physics of semiconductors and that of nanocomposites: Electron-hole duality. The “P=1/8” anomaly in YBa2Cu3O6+x is caused by the simultaneous presence of electrons and holes, a consequence of incomplete electron transfer.

First-Principles Studies for Magnetism in Cu-Doped GaN

Hole carrier mediated magnetization in Cu-doped GaN is investigated by using the first-principles calculations. By studying the sp-d interaction and the direct exchange interaction among the dopants, we obtain an equation to determine the spontaneous magnetization as a function of the Cu dopant concentration and the hole carrier density. It is demonstrated that nonmagnetic Cu doped GaN can be of room-temperature ferromagnetism. The system＇s Curie temperature Tc can reach about 345 K with Cu concentration of 1.0% and hole carrier density of 5.0×10^19 cm-3. The results are in good agreement with experimental observations and indicate that ferromagnetism in this systems is tunable by controlling the Cu concentration and the hole carrier density.