arXiv subjects

A. V. Fetisov

Publications and source records attributed to A. V. Fetisov.

11 recordsLinked to original sources

arXiv2026

An echo of the low-temperature phase competition and 1/8 dip in room-temperature properties of cuprate HTSCs

Cuprate high-temperature superconductors (HTSCs) exhibit a characteristic dome-shaped dependence of the superconducting transition temperature on the charge carrier concentration, Tc(p), featuring a maximum at optimal doping p = 0.16. Near the p = 1/8 composition, a sharp suppression ("dip") of Tc occurs - conventionally referred to as the "1/8 anomaly" - which is widely attributed to charge and spin ordering in the CuO2 planes. Here, we investigate the room temperature hydration of La2-xBaxCuO4 and YBa2Cu3O6+delta under a high-frequency magnetic field and report anomalous weight changes during the initial stage of the process. For both compounds, the doping dependence of these weight fluctuations closely mirrors their respective Tc(p) profiles, including the signature "1/8 anomaly". The prominent manifestation of these characteristically low-temperature electronic features at room temperature provides critical insights into the stability of high-energy electronic correlations. These findings may offer a novel foundation for the development of theoretical models of cuprate superconductivity.

cond-mat.supr-con↗

arXiv2025

New experimental evidence for Podkletnov effect

In the works of E. Podkletnov et al. (for example [Physica C: Superconductivity, 1992, Vol. 203, p. 441]), a unique experiment is described in which a significant reduction in the weight of various test bodies was observed when placed above a rotating disk made of the superconductor YBa2Cu3O6+delta (YBCO); the disk was in the superconducting state (at 20-70 K) and was subjected to an alternating (50 Hz-100 MHz) magnetic field. Numerous attempts to replicate this experiment in other laboratories have been unsuccessful; however, a broad discussion has been initiated regarding the possible nature of the "Podkletnov effect" - the weight loss of objects located above the superconductor. In the present experimental work, results similar to the Podkletnov effect have been obtained, which, however, occur at room temperature. During our experiments, gas-tight containers with the crystal hydrate K2CO3X1.5H2O and dispersed YBCO exhibited a sharp loss of part of their weight during and after 0.5 hours of exposure to a magnetic field with a frequency of 50 MHz. Changes in the weight of various test bodies located in close proximity to the containers were recorded. It was found that these weight changes correlate with the external surface area of the bodies and do not depend on their chemical nature. A dependence of the magnitude of weight changes on the oxygen content in YBCO was obtained, which shows a significant dip in the region where superstructural orderings of the oxygen sublattice exist in the basal plane. This dip coincides in shape with the well-known dip in the dependence of Tc on delta (the "60-K plateau"). The possible connection between these two extraordinary phenomena coexisting in YBCO compounds - inexplicable weight changes and high-temperature superconductivity - is discussed.

cond-mat.supr-con↗

arXiv2020

Puzzling behavior of hydrated YBCO

We study the influence of a close-lying non-magnetic and non-charged metal disk on the hydration reaction of YBa2Cu3O6+d (YBCO). It has been established, that at a distance in the range of 6 - 7 mm from the disk surface, the rate of the hydration is significantly reduced relative to distances out of this interval. This effect has allowed us to assume that there is an interaction between YBCO and the disk the nature of which is still unknown. Further direct measurements of the force acting between these bodies have been performed. A recorded repulsive interaction with a magnitude of 6.5*10-6 N, which is 0.04% of the sample weight, has confirmed our assumption.

cond-mat.mtrl-sci↗

arXiv2019

Distance to massive metal body -- a paradoxical parameter that regulates the intensity of the hydration of YBa$_2$Cu$_3$O$_{6.75}$

As known, external fields can have a noticeable effect on a number of processes such as recombination of radicals, processes occurring in biological systems, some processes of adsorption, etc. However, there are no any mentions in literature about the impact on chemical processes of non-magnetic and non-charged bodies which do not have direct contact with the reagents. In the current study we examine the effect on the hydration of YBa2Cu3O6.75 (YBCO) of a closely placed non-magnetic and non-charged steel disk. For this purpose we utilize a previously developed special method of material preparation that has been published earlier. The resulting material we analyze by the iodometric titration technique, X-ray diffraction, and X-ray photoelectron spectroscopy. Conducting the experiment on a large number of the YBCO samples being hydrated at different distances from the disk clearly indicates a significant inhibitory effect of this factor. We find that there is a certain distance from the surface of the metal body, at which the hydration process achieves maximum sensitivity to the metal presence. At this stage of research, it is assumed that the mediator, with the aid of which the influence on the hydration process occurs, might be electromagnetic radiation emanating from the YBCO samples during their hydration and reflected from the surface of metal.

cond-mat.mtrl-sci↗

arXiv2018

Evolution of electronic and crystal structure during room-temperature annealing of quenched REBa2Cu3O6+d, RE=Y, Nd

The crystal structure parameters and the low-temperature magnetic moment of the HTSC cuprates YBa2Cu3O6+d, Y1-xCaxBa2Cu3O6+d, and Nd1+xBa2-xCu3O6+d, x = 0.2 are recorded after quenching them from the temperature of oxidative annealing. The subject of the present study is the aging effect, which results in an increase in the critical temperature Tc and a decrease in the c parameter of the crystal lattice for a while after the quenching. On the example of YBa2Cu3O6+d, it is shown that the oxygen content dependence of c undergoes the following changes with time: (1) there is an increase in the dependence slope with respect to the (6+d)-axis; (2) there is an increase in the dependence nonlinearity. The first type of changes is explained by an increase in the valence of copper ions in the CuOd planes that is accompanied by a decrease in their radius. The second type is explained by the electrostatic interaction of the CuO2 structural planes due to the accumulation on them electron holes. Calculation of the parameter c changes shows good quantitative agreement with the experimental data. The data obtained for the compounds Y1-xCaxBa2Cu3O6+d, and Nd1+xBa2-xCu3O6+d (the cases of the hole and electron doping of CuO2-planes) are discussed on the basis of the model representation developed by us for YBa2Cu3O6+d.

cond-mat.mtrl-sci↗

arXiv2017

Vicinity effect of massive bodies on YBa2Cu3O6+d being saturated with air components

We study the influence of the close-lying massive bodies on the YBCO material while it is being saturated with air components. It has been found the effect that can be interpreted as attraction/repulsion of the bodies to/from the samples of hydrated YBCO. This force interaction has been confirmed by a "direct" dynamometric method for the Earth as a maximum massive body to be used in our experiments.

physics.gen-ph↗

arXiv2017

XPS study of the chemical stability of DyBa2Cu3O6+δ superconductor

The chemical stability of the powder DyBa2Cu3O6+δ has been studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and thermal analysis at ambient conditions. The powder was subjected to mechanical processing in a ball mill-activator to accelerate chemical degradation. The kinetic regularities of hydrolytic decomposition of DyBa2Cu3O6+δ under the influence of air moisture have been determined. The resistive properties of DyBa2Cu3O6+δ to water have been found to be better, but not much different from analogous properties of YBa2Cu3O6+δ which is unstable in a wet environment. Chemical degradation of the material is triggered by crucial concentrating of water particles near the free surface of the solid reactant (due to their low diffusibility in the bulk) leading to rapid chemical decomposition of the respective regions.

cond-mat.mtrl-sci↗

arXiv2017

On the room-temperature aging effects in YBa2Cu3O6+d

The aging effects in YBa2Cu3O6+d have been investigated on the low-speed quenched samples in contrast to other similar studies where the high-speed quenched samples were examined. In the framework of the investigation, XPS analysis has been conducted for the samples stored after quenching for the specified times t and a detailed experimental dependence of the YBa2Cu3O6+d lattice parameters a, b, and c on both d and t has been obtained. The regime of low-speed quenching results in a threefold increase in the aging effect magnitude. Particular cases of the c(d; t) dependence are well described by a second-order polynomial with applying different coefficients for different t. The behavior c has been explained on the basis of a simple model of the Coulomb interaction between the CuO2 and CuOd structural planes, in which the hole charge transfer from CuOd to CuO2 takes place providing the standard level of Tc in YBa2Cu3O6+d (this level is characterized by a maximum Tc of 93 K at d = 0.9). It has been demonstrated that the c(d; t) dependence is a good alternative to assessing the hole concentration in YBa2Cu3O6+d. By analyzing the c(d; t) experimental dependence as well as the data on the hole localization in the pairs Cu-O obtained by XPS, the authors have made a conclusion about the nature of observed aging effects. The latter are likely to be related to the transition of the Cu 3d9L-1 electron configuration to Cu 3d8 for copper in the basal plane of YBa2Cu3O6+d at RT.

cond-mat.mtrl-sci↗

arXiv2017

Relationship between electronic and crystal structure in Nd1+xBa2-xCu3O6+d

In accordance with a relation between the lattice parameter c and the concentration of holes p, which has been found earlier for the YBa2Cu3O6+d compound, we obtain the p parameter in the same manner for the solid solution Nd1.2Ba1.8Cu3O6+d with substitution of Nd3+ for Ba2+ in barium sites. For this, structural and superconducting properties of the Nd1.2Ba1.8Cu3O6+d samples stored for specified times t after quenching from annealing temperatures have been studied. The investigation shows that Nd1.2Ba1.8Cu3O6+d stored for a long time has quite a low critical temperature Tc extending only to Tconset = 55 K for the most oxidized sample with d = 0.953. We find that the d-dependence of the lattice parameter c significantly changes with time t. When using the relation between c and p, the existence of electron doping of 0.045 per Cu in Nd1.2Ba1.8Cu3O6+d can be inferred. This doping explains well reduced Tc in Nd1.2Ba1.8Cu3O6+d. In addition, we observe a local drop of Tc by up to 20 K for the samples with p ~ 0.095 (d ~ 0.8) similar to decreasing Tc known as "anomaly 1/8".

cond-mat.mtrl-sci↗

arXiv2017

YBa2Cu3O6+d-originated attraction force giving rise to Meissner effect at 300 K

The exposure of YBCO to an air atmosphere at first at pH2O = 110 Pa and then at pH2O = 1 kPa has been used for uncharacteristic and unusual properties of YBCO to be observed. Among them there was an increased reactivity of YBCO with respect to water. Besides, it was experimentally obtained extremely excessive weight gain of hydrated YBCO samples that was not corresponding to the quantity of the absorbed water. Finally, we obtained the significant negative value of the room-temperature (RT) magnetic susceptibility in conventional magnetic study of the hydrated YBCO that was confirmed by the direct observation of decreasing weight of the same samples that were suspended above the source of controlled magnetic field (DC mode) at RT. All the results were explained on the basis of an approximate idea that there is a certain source of attractive force inside YBCO, acting on surrounding particles and bodies.

cond-mat.mtrl-sci↗

arXiv2009

The effect of anomalous adsorption of H2O and CO2 by pre-hydrated YBa_2Cu_3O_{6.53}

The results of a comprehensive study on the YBa_2Cu_3O_{6.53} oxide subjected to "mild" hydration (exposure at small values of pH2O) by a special technique have been reported. The material modified in this way acquires an interesting property; namely, in natural conditions it intensively absorbs large quantities of components (H2O and CO2) comprising the gas atmosphere. Arguments have been adduced that at least the water enters the crystal lattice of the yttrium-barium cuprate. This lattice is in the two-phase (tetragonal and orthorhombic) state: testing of the magnetic properties of the oxide has revealed the presence of antiferromagnetic and diamagnetic regions in this material.

cond-mat.mtrl-sci↗