arXiv subjects

A. V. Krevsun

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

17 recordsLinked to original sources

arXiv2026

High-Temperature Superconductivity of the Fe-Se-H compound

Using an EPR spectrometer, the dependences of microwave power absorption on magnetic field up to 6000 Oe were measured at temperatures of 3.6-25 K and 295 K in a powdered compound Fe-Se-H, obtained by thermal diffusion of hydrogen into a FeSe single crystal with a critical temperature of 8 K. The shape of the dependences and the analysis of the measurement results confirm the superconductivity of the Fe-Se-H compound at normal pressure, both at temperatures of 3.6-25 K and at 295 K, i.e., at room temperature.

cond-mat.supr-con↗

arXiv2026

Determination of the properties of a superconducting single crystal FeSe using an EPR spectroscopy

Using an EPR spectrometer, the properties of single-crystal FeSe were studied in a magnetic field up to 6000 Oe at temperatures from 3.5 K to 8 K in the superconducting state and at temperatures above 8K and up to 25K in the normal state. It was shown that by measuring non-resonant spectrometer signals in zero and weak magnetic fields up to 30 Oe, it is possible to determine critical temperature Tc, the superconducting transition width, and the value of the first critical magnetic field Hc1 in FeSe single-crystal. Resonant EPR signals are observed in fields at 1400 Oe and 3400 Oe, which corresponds to the paramagnetism of doubly ionized iron atoms (Fe2+) in the FeSe crystal. Non-resonant EPR signals in a magnetic field up to 6000 Oe at temperatures from 3.5K to 8K are a nonlinear function of the field, and correspond to the superconducting mixed state of the FeSe, but at temperatures above 8K (up to 25K) they are field independent.

cond-mat.supr-con↗

arXiv2024

Hydrogen in superconductors

Information is presented on the state of research on the effect of hydrogen on the superconducting properties of various compounds. The review consists of an introduction, one appendix and four sections: methods for the synthesis of modern hydrogen-containing superconductors, experimental studies of the properties of hydrogen-containing superconductors, on the mechanisms of the influence of hydrogen on superconductivity, problems and prospects of hydrogen-containing superconductors.

cond-mat.supr-con↗

arXiv2023

Features of nanocontact formed using point electrical breakdown of a niobium oxide nanolayer

The electrical characteristics of a point section of niobium oxide between a massive cathode made of a superconducting indium-tin alloy and a niobium film before the oxide breakdown and the nanocontact that appears after the breakdown of the oxide at room temperature have been studied. The dependences of the point breakdown voltage of the oxide and the resistance of nanocontacts on the method of breakdown and the thickness of the oxide in the range of 15-60 nm have been established. In particular, a minimum value of the breakdown current has been established (about 1 μA), below which breakdown does not occur. The voltage-current characteristic (VCC) of the oxide has a semiconductor character and indicates the dependence of the breakdown voltage of the oxide on its polarity. The VCC of the nanocontact is nonlinear, which is associated with phase transitions in the nanocontact material caused by its heating by the transport current.

cond-mat.supr-con↗

arXiv2022

Combined breakdown of a dielectric nanolayer to form a Josephson bridge

Electrical breakdown of a dielectric nanolayer between film electrodes under the combined action of direct current and capacitor discharge current makes it possible to form Josephson bridges with a reproducible resistance exceeding 1 Ω. A new feature of the formation of a bridge during electrical breakdown, which is preceded by a series of preliminary breakdowns (auto breakdowns) of a dielectric nanolayer, has been discovered. The mechanism of the process and the role of the thickness of the cathode film in the formation of the bridge are discussed.

cond-mat.supr-con↗

arXiv2022

Superconducting source and sensor of single bubbles to study nucleate boiling of liquid helium

Joule heat generated by resistive elements of cryogenic micro- and nanodevices often originates boiling of the cooling cryogenic liquids (helium, nitrogen). The article proposes an experimental method to explore the dynamics of the formation and development of a single vapor bubble in cryogenic liquid by sensing the temperature change of a superconducting thin-film microbridge being in the resistive state with single phase-slip center or line. It serves both the source of heat for generating single bubbles and the surface temperature sensor due to its temperature-dependant excess current. The average bubble detachment rate and the average single bubble volume were experimentally determined for nucleate helium boiling. The obtained values are in good agreement with the data of other authors found in literature.

cond-mat.supr-con↗

arXiv2022

Electrical breakdown of a dielectric for the formation of a superconducting nanocontact

Electrical breakdown of the dielectric nanolayer between film electrodes of niobium and an alloy of 50% indium and 50% tin forms a bridge of this alloy between the electrodes. The bridge resistance depends on the breakdown current. The length of the bridge is equal to the thickness of the dielectric (30 nm), and its diameter is 25 nm. The calculated coherence length of the alloy at 0 K is close to the length of the bridge. The calculated critical current of a bridge with a resistance of 1 Ω at a temperature of 0 K is 2 mA. It is concluded that such a bridge should have the properties of a Josephson contact at a temperature lower than the critical temperature of the alloy (6.5 K).

cond-mat.supr-con↗

arXiv2019

Study of electrical conductivity of the coatings of bimetallic Au-Ag nanoparticles

The "metallic" temperature variation of the electrical resistivity of chemical nano gold-silver coatings with a silver content of 6.6 % at. up to 13.1 % at. determined in the temperature range 4.2-300 K. Features of low-temperature measurements of the resistance of nano-coatings were found and explained. The possibility of the appearance of superconductivity in them is discussed.

physics.app-ph↗

arXiv2018

The effect of alternating current on the current states of a quantum interferometer shunted by a superconducting inductance

The patterns of reversible changes in the critical current and discrete current states of a structure in the form of a superconducting quantum interferometer shunted by superconducting inductance, as a result of passing an alternating transport current through the structure and applying an external alternating magnetic field simultaneously with a direct transport current, was established. A new type of discrete stationary state was discovered during the transition of the interferometer to the resistive state caused by the combined action of direct and alternating transport currents.

cond-mat.supr-con↗

arXiv2018

High-temperature superconductors of the family (RE)Ba2Cu3O7-delta and their application (Review Article)

This review article is a commemoration of the 30th anniversary of the discovery of YBa2Cu3O7-delta high-temperature superconductors (HTSCs). As a result of this discovery a family of (RE)Ba2Cu3O7-delta (RE stands for "rare earth") HTSCs has found great practical use. The review article consists of a brief history of how YBa2Cu3O7-delta was conceived and five sections describing the family of compounds: crystallography, phase diagrams, manufacturing techniques, main superconducting properties, and fields of application.

cond-mat.supr-con↗

arXiv2018

Thin film superconducting quantum interferometer with ultralow inductance

A simple method has been developed for manufacturing a thin film superconducting quantum interferometer (SQI) with ultralow inductance (~10^-13 H). Current-voltage and voltage-field characteristics of the SQI are presented. The basic design equations are obtained and confirmed experimentally. The SQI has been used for the first time to determine the penetration depth of a magnetic field into a film of 50% In-50% Sn alloy.

cond-mat.supr-con↗

arXiv2015

Measurement of energy gaps in superconductors by means of quantum interference devices

The effect of temperature on the form of discrete changes in the current in highly inductive (~10-6 H) doubly-connected superconductors with niobium-niobium clamped point contacts is determined experimentally. The magnitude and duration of the voltage pulse on a doubly-connected superconductor is measured at the time of the discrete change in its current state. The pulse magnitude is close to the energy gap 2D/e of the superconductor and its duration (~10-6 s) corresponds to the minimum possible time (~10-12 s) for a change in the state of the contact when the depairing current through it is reached. The measurement data are discussed in terms of models of the quantum interference of currents in a doubly-connected superconductor with clamped point contacts in the form of a quantum interferometer.

cond-mat.supr-con↗

arXiv2014

Current states of a doubly connected superconductor with film bridges

Transport current distribution in the branches of a doubly connected superconductor in the form of a thin-film high-inductance circuit with two bridges of different width in the branches was measured. For the transport current lower than the sum of critical currents of the bridges, its distribution was found to exhibit an anomalous behavior upon reaching the critical current of one of the bridges. For a fixed value of the transport current through the circuit higher than the sum of critical currents of the bridges, low-frequency continuous harmonic voltage self-oscillations together with synchronous current self-oscillations appeared in the circuit branches. The mechanism responsible for the onset of the self-oscillations is discussed.

cond-mat.supr-con↗

arXiv2013

Detection of self-oscillations of the transport current in a doubly connected superconductor

It has been found experimentally that when dc current is passed through a circuit consisting of two superconductors connected in parallel and reaches its critical value in one of the circuit branches the current in the branches undergoes quasi-harmonic undamped oscillations. The mechanism resulting in the appearance of the self-oscillations is discussed. The characteristics of magnetic field freezing in a circuit with self-oscillating current are examined.

cond-mat.supr-con↗

arXiv2013

Freezing and quantization of current passing through a doubly connected superconductor with a point contact

The particulars of dc current passage through a structure consisting of a doubly connected superconductor (DCS) with branches that are asymmetric with respect to length and critical current have been investigated experimentally. The short branch, which has the lowest critical current, was a clamping niobium-niobium point contact with length comparable to the coherence length of the superconductor. In contrast to a previously studied DCS with a short branch much longer than the coherence length, it was found that when the short-branch current reaches the critical value the currents in the branches of the DCS do not undergo self-excited oscillations; a current exceeding the critical value enters the long branch when this current is increased in portions (is quantized), and when it is subsequently decreased it freezes partially or completely in the DCS circuit.

cond-mat.supr-con↗

arXiv2013

Current states of a doubly connected superconductor with two point contacts

The distribution of the transport current in branches of a doubly connected superconductor (DCS) with two clamping point contacts is investigated experimentally when the contacts are in the different states: (a) one or both contacts are in the critical state, (b) both are in the supercritical (resistive) state. In the state (a) the transport current frozen in the DCS and injected through one of the contacts can be increased or decreased by tuning the value and polarity of the current passing through the other contact. In the state (b), the current self-oscillations the amplitude and the frequency of which depend on the value of the injected transport current appear in the branches of the DCS. A role of the parametric Josephson inductance and resistivity of the contact in formation of its critical state and in distribution of the current in the branches of the DCS is discussed.

cond-mat.supr-con↗

arXiv2013

Quantization of diamagnetic current in a superconducting ring with the Josephson point contact

It was established experimentally that a critical value of the diamagnetic current, excited by an external magnetic field in a superconducting ring (with an inductance of about ~ 10^-6 H) with a Nb-Nb clamping point contact having the Josephson contact properties is a strictly periodic function of field strength, despite the complex microstructure of the clamping contact. The reasons of the periodic dependence are discussed on a basis of the interference model of diamagnetic current and quantized values of the circulating current in the microinterferometer formed by the clamping contact.

cond-mat.supr-con↗