arXiv subjects

V. I. Kuznetsov

Publications and source records attributed to V. I. Kuznetsov.

At least 19 recordsLinked to original sources

arXiv2026

Unusual critical currents in quasi-one-dimensional superconducting aluminum two-width structures in a magnetic field

We measured unusual critical currents as functions of temperature in the zero field and as functions of a magnetic field perpendicular to the substrate surface at a given temperature close to the critical temperature in thin-film long quasi-one-dimensional superconducting aluminum two-width structures consisting of narrow and wide wires with different critical temperatures. It is found that the experimental critical switching current as a function of the field at a given temperature, determined by the appearance of a dc voltage on a short section of the structure, is nonlocal (dependent on electron transport in the area containing the junction line between the narrow and wide wires). When current flows through the narrow and wide wires of the structure, the switching currents, experimental and calculated within the framework of the Ginzburg-Landau theory, differ radically from each other. A nonzero switching current exists in high fields greater than the maximum critical magnetic field in a quasi-one-dimensional superconducting wire. In the aluminum two-width structures studied here, the unusual measured switching current challenges description by known theories.

cond-mat.supr-con↗

arXiv2026

Shift of the maxima of the critical currents of different polarity relative to the zero magnetic flux along the flux axis in a superconducting asymmetric aluminum ring

We measured the rectification of an ac voltage in a structure of superconducting circularly-asymmetric aluminum rings in series, permeated with a magnetic flux and biased with a low-frequency alternating current (without a dc component). This rectification is due to the shift of the maxima of the critical currents of different polarity relative to the zero flux in opposite directions along the flux axis in the asymmetric ring. For the first time, we propose a model for a temperature-dependent phase shift equal to difference between dimensionless kinetic inductances of wide and narrow semirings having the same length and thickness. The shift is not zero in the case of different critical currents densities in both semirings. This is possible only in a situation of different critical temperatures of both semirings. The model describes well the temperature-dependent shift of the maxima of the critical currents, answers the long-standing mysterious challenge of the shift and removes extremely strange contradiction between the results of different measurements, previously found in circularly-asymmetric aluminum structures.

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arXiv2026

Critical temperatures and critical currents of wide and narrow quasi-one-dimensional superconducting aluminum structures in zero magnetic field

We measured the critical temperatures and critical switching and retrapping currents of wide and narrow thin-film quasi-one-dimensional superconducting aluminum structures of the same thickness in zero magnetic field. For the first time, we found that the narrower the structure, the lower the critical temperature and critical current density in the structure. Probably, the influence of depairing centers that are on dirty longitudinal boundaries of the structure, is the stronger than the narrower the structure. It is found for the first time that, in most cases, the temperature-dependent switching critical current in both structures is approximated by two functions. At temperatures below the temperature corresponding to the bottom of the resistive N-S transition of structures, the switching critical current is described by the Kupriyanov-Lukichev theory. At temperatures close to the top of the N-S transition, the switching current is linear with temperature and coincides with the critical Josephson current. At these temperatures, Josephson SNS junctions are formed in structures.

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arXiv2026

Negative nonlocal and local voltages (resistances) in a quasi-one-dimensional superconducting aluminum structure

To study a nonlocal electron transport in an aluminum superconducting quasi-one-dimensional structure, we measured negative nonlocal (local) direct current voltages in the structure in a magnetic field near the critical temperature. The structure is a normal-superconducting at $T_{cn}<T<T_{cw}$ ($T_{cn}$ and $T_{cw}$ are the critical temperatures for narrow and wide wires, respectively, making up this structure). Negative voltage arises due to a quasiparticle current flowing through the N-S interface. We plotted the experimental and theoretical temperature and magnetic-field dependences of current, resistance and voltage corresponding to the peak of negative voltage, taking into account either equilibrium or nonequilibrium superconducting fluctuations.

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arXiv2019

Voltage plateaus on V(I) curves of long quasi-one-dimensional superconducting wires (without microwave irradiation)

Almost constant voltage plateaus on the V(I) curves of long quasi-one-dimensional superconducting aluminum wires placed in magnetic field at temperatures T slightly below the critical superconducting temperature Tc were found which were unexpected for the sample geometry and parameters of the experiment. The plateaus are assumed to be subharmonics of a superconducting gap and arise due to the multiple Andreev reflection and strong quasiparticle overheating in the wire nonequilibrium region. The plateaus are evidence of coexistence of superconductivity and dissipation in such wires. The results presented in the paper could not be described by existing theories.

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arXiv2019

Quantum magnetoresistive (hc/2e)/m periodic oscillations in a superconducting ring

It was experimentally found that quantum magnetoresistive hc/2e periodic oscillations of the Little-Parks type in a superconducting mesoscopic ring with decreasing temperature and increasing applied dc current are modified to the sum of harmonic (hc/2e)/m periodic oscillations. Multiple Andreev reflection can be a possible cause of this effect.

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arXiv2013

Unusual quantum magnetic-resistive oscillations in a superconducting structure of two circular asymmetric loops in series

We measured both quantum oscillations of a rectified time-averaged direct voltage V_{rec}(B) and a dc voltage V_{dc}(B) as a function of normal magnetic field B, in a thin-film aluminum structure of two asymmetric circular loops in series at temperatures below the superconducting critical temperature T_{c}. The V_{rec}(B) and V_{dc}(B) voltages were observed in the structure biased only with an alternating current (without a dc component) and only with a direct current (without an ac component), respectively. The aim of the measurements was to find whether interaction (nonlinear coupling) exists between quantum magnetic-resistive states of two loops at a large distance from each other. The distance between the loop centers was by an order of magnitude longer than the Ginzburg-Landau coherence length ξ(T). At such distance, one would not expect to detect any interaction between the quantum states of the loops. But we did find such an interaction. Moreover, we found that V_{dc}(B) functions (like V_{rec}(B) ones) can be used to describe the quantum states of the loops.

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arXiv2011

Segment of an inhomogeneous mesoscopic loop as a dc power source

A dc voltage changed periodically with magnetic field is observed on segments of asymmetric aluminum loop without any external dc current at temperatures corresponded to superconducting transition. According to this experimental result a segment of the loop is a dc power source. A possibility of a persistent voltage on segments of an inhomogeneous normal metal mesoscopic loop follows from this result.

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arXiv2008

Rectified dc voltage versus magnetic field in a superconducting asymmetric figure-of-eight-shaped microstructure

We have measured periodic oscillations of rectified dc voltage versus magnetic field V_{dc}(B) in a superconducting aluminum thin-film circular-asymmetric figure-of-eight microstructure threaded by a magnetic flux and biased with a sinusoidal alternating current (without a dc component) near the critical temperature. The Fourier spectra of these V_{dc}(B) functions contain fundamental frequencies representing periodic responses of the larger and smaller asymmetric circular loops, composing the microstructure, to the magnetic field. The higher harmonics of the obtained fundamental frequencies result from the non-sinusoidal character of loop circulating currents. The presence of the difference and summation frequencies in these spectra points to the interaction between the quantum states of both loops. Magnitudes of the loop responses to the bias ac and magnetic field vary with temperature and the bias current amplitude, both in absolute values and with respect to each other. The strongest loop response appears when the average resistive state of the loop corresponds to the midpoint of the superconducting-normal phase transition.

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arXiv2007

Asymmetry with respect to the magnetic field direction in the interaction between the quantum states of two coupled superconducting rings

The interaction between the quantum states of two aluminum superconducting rings forming an 8-shape circular-asymmetric microstructure was examined under a threading magnetic flux and bias by an alternating current without a dc component. Quantum oscillations of the rectified dc voltage Vdc(B) as a function of magnetic field were measured in the 8-shape microstructure at various bias ac currents and temperatures close to critical. Fourier and wavelet analyses of Vdc(B) functions revealed the presence of various combination frequencies in addition to two ring fundamental frequencies, which suggests the interaction in the structure. Deviation of the Vdc(B) function from oddness with respect to the magnetic field direction was found for the first time.

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arXiv2007

Quantum oscillations of rectified dc voltage as a function of magnetic field in an "almost" symmetric superconducting ring

Periodic quantum oscillations of a rectified dc voltage Vdc(B) vs the perpendicular magnetic field B were measured near the critical temperature Tc in a single superconducting aluminum almost symmetric ring (without specially created circular asymmetry) biased by alternating current with a zero dc component. With varying bias current and temperature, these Vdc(B) oscillations behave like the Vdc(B) oscillations observed in a circular-asymmetric ring but are of smaller amplitude. The Fourier spectra of the Vdc(B) functions exhibit a fundamental frequency, corresponding to the ring area, and its higher harmonics. Unexpectedly, satellite frequencies depending on the structure geometry and external parameters were found next to the fundamental frequency and around its higher harmonics.

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arXiv2004

Thin-Film Aluminum Microstructure as a Hot-Electron Microwave Radiation Detector

We have found that the thin film aluminum structures shaped into a chain of micron sized islands connected by narrow isthmuses, can modify their electrical and structural properties under microwave radiation. As a result, at the temperature of 4.2 K the film structures turn into a kind of lateral periodic structure N-S-N, where N is for normal islands, S is for superconducting isthmuses. Current-voltage characteristics of the samples, as well as changes of these characteristics under low power radiation, have been studied over the temperature range from 1.3 to 10 K. The sensitivity of a structure as a microwave detector runs 10^{5} V/W.

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arXiv2004

Temperature dependence of the resistance of a phase-slip line in a thin superconducting film

An experimental investigation was made of the temperature dependence of the first step of a phase-slip line in a thin superconducting tin film. The depth of penetration of a nonequilibrium longitudinal electric field into the superconductor was determined near the critical temperature. A comparison was made with theoretical investigations of one-dimensional structures containing phase-slip centers. The experimental results were found to be in good agreement with the theory when the mechanism of mixing of electron-like and hole-like branches of the quasiparticle spectrum was governed by the elastic scattering of the excitations. This was one more experimental confirmation that a phase-slip line is a two-dimensional analog of a phase-slip center.

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arXiv2004

Induction of phase-slip lines in a thin, wide superconducting film by an rf electromagnetic field

The appearance of phase-slip lines, induced by an rf field, was observed experimentally in wide superconducting films in which the destruction of superconductivity by a dc current is associated with the formation of phase-slip lines. The characteristics of the separation of the film into superconducting and nonuniform, isothermal, nonequilibrium regions (phase-slip lines) under electromagnetic irradiation were studied.

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arXiv2004

Synchronization of high-frequency oscillations of phase-slip centers in a tin whisker under microwave radiation

Current-voltage characteristics of a system with a variable number of phase-slip centers resulting from phase separation in a tin whisker under external microwave field with a frequency Ω/2π\=35-45 GHz have been studied experimentally. Emergence and disappearance of steps with zero slope in a whisker's current-voltage characteristic at U_{m/n}=(m/n)U_Ω, where m and n are integers and U_Ω is determined by Josephson's formula \hbarΩ=2eU_Ω, have been investigated. Microwave field generated by phase-slip centers is nonharmonic, and the system of phase-slip centers permits synchronization of internal oscillations at a microwave frequency by an external field with a frequency which is the n-th harmonic of internal oscillations. The estimated microwave power generated by a whisker is 10^{-8} W. Stimulation of superconductivity in a current-carrying whisker has been detected.

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arXiv2004

Observation of a nonmonotonic transverse voltage induced by vortex motion in a superconducting thin film

A vortex-induced transverse voltage in a superconducting film, previously predicted theoretically, has been seen experimentally for the first time. The magnitude of this voltage and its nonmonotonic current dependence are explained on the basis of a curvature of the trajectory of vortices resulting from their interaction. A good agreement between theory and experiment is found.

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arXiv2004

Conversion of phase-slip lines into elementary resistive domains in a current-carrying superconducting thin film

A nonmonotonic dependence of the differential resistance of the first step of a phase-slip line on the heat-reservoir temperature near Tc has been observed experimentally for the first time in a superconducting tin film. This behavior is interpreted as a conversion of the phase-slip line into an elementary resistive domain as the result of a deviation from the isothermal conditions.

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arXiv2003

Quantum voltage oscillations observed on segments of an inhomogeneous superconducting loop

A theoretical prediction published in Phys.Rev. B 64, 012505 (2001) is corroborated experimentally. This corroboration of the theoretical result published in Physical Review B was rejected for publication in the same journal. Such inconsistency is connected with a contradiction to the second law of thermodynamics. According to the theory Phys.Rev. B 64, 012505 (2001) the energy of a noise can be transformed to a dc power in superconducting loop and therefore a dc voltage oscillating with magnetic field can be observed on segments of an inhomogeneous loop in the temperature region close to the superconducting transition. Such quantum voltage oscillations observed in the present work can be induced both by an external electrical noise and by internal equilibrium noise (thermal fluctuations). Violation of the second law takes place in the second case. First of all the theoretical result published by Phys.Rev.B is challenge to the second law but about this contradiction was openly written only in the first version (see physics/0105059) of the experimental paper rejected by Referees of Phys.Rev.B. The transformation of an external electrical noise to the dc voltage was confirmed recently in the paper published in JETP Letters 77, 371 (2003) (see also cond-mat/0303538).

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