Mikhail Belogolovskii

National Academy of Sciences of Ukraine | ISP · G. V. Kurdyumov Institute for Metal Physics

We have fabricated and characterized all-MoGe Josephson junctions with a very thin Al/AlOx/(Al) barrier, where the amorphous MoGe films exhibit superconducting transition temperatures up to 7 K. Due to the uniformity of the surface morphology of the MoGe films, the junctions demonstrate high uniformity of their tunneling properties. The experimenta...

The origin of anomalous current-carrying edge states in quasi-two-dimensional quantum samples with an insulating interior is currently mysterious. We propose to address this issue using a hybrid setup, an interferometric phase-sensitive configuration of two independent scanning probe tips, normal and superconducting, able to realize the quantum int...

Point-contact Andreev spectroscopy is one of the most powerful techniques for obtaining quantitative energy and momentum-resolved information on the electronic properties of a superconductor. However, appropriate measurements often reveal unexpected conductance features that cannot be adequately modeled using conventional theory. In particular, the...

We report experimental studies of quantum-matter heterostructures based on a ferromagnet/normal metal multilayer proximitized by Nb superconducting electrodes to form a novel Josephson weak-link device that is highly sensitive to magnetic fields. The device is a single Josephson junction containing Al/Ni or Al/Py (Py: Ni <sub xmlns:mml="http://www....

An observed correlation between the critical temperature of a superconducting transition in high-temperature superconductors and a proximity of their electronic structure to the topological Lifshitz transition needs to be verified on simple model materials. Here we show that such an object could be a Mo–Re alloy with an equal concentration of const...

Time-dependent electron current through a nanoscale phase-coherent quantum ring with leads, coupled to reservoirs biased by a sinusoidal voltage, is studied. We argue that Floquet states in such samples, driven also by external time-periodic magnetic field, can be coherently manipulated. Some examples show that on-demand structures in the frequency...

Penetration of Cooper pairs from a superconducting layer to a ferromagnetic one in superconductor–ferromagnet contacts, known as a proximity effect, has been a subject of intensive research over the past few decades. At the beginning of the century, it became clear that the proximity effect is supplemented by a reverse influence of the magnetic mat...

In this work, we realize a physical system—nanoengineered singly connected Josephson junction with a periodic superparamagnetic Ni/Al multilayer—that manifests supercurrent-versus-magnetic field response typical of a dc superconducting quantum interference device (SQUID); however, unlike a SQUID, which involves a superconducting loop occupying sign...

We start with a short look at the problem of low-capacitance Josephson junctions, its history, and actual state-of-the-art. It is argued that such devices are important for applications requiring nonhysteretic current-voltage characteristics since reduction of capacitance by several times makes it possible to increase the device resistance by the s...

Understanding electronic noise in hybrid junctions is essential for designing efficient nanoscale electronics at the quantum limit. Recently, a new (previously overlooked) noise contribution, generated by the temperature difference across a conducting heterostructure and denoted as delta-T noise, was predicted and revealed experimentally in atomic-...

Expectation of fundamentally new phenomena owing to multiband superconductivity stimulates a search for novel materials with, at least, two distinct gaps in the superconducting state. Recent temperature-dependent electronic heat capacity and lower critical field measurements for molybdenum-rhenium alloys have revealed signatures of two-gap supercon...

The Josephson effect, as an example of a macroscopic quantum phenomenon, reveals itself in the three-layer heterostructures formed by two superconductors coupled by a weak link that usually consists of a 1–2 nm-thick insulating barrier. The traditional way of modelling such-systems’ dynamics is based on an equivalent circuit that comprises three pa...

Great practical needs motivated extensive efforts to discover ultra-low resistance electrical conductors and/or superconductors. Herein we report the observation of a vanishingly small electrical resistance at the ambient temperature and pressure in carbon nanostructured compounds obtained in a hybrid helicon-arc ion-plasma reactor developed by the...

Hereafter, we present our results on the implementation of aluminum nitride (AlN) as a promising thermal interface material for improving heat performance of high-power micro- and nanoelectronic devices. The efficiency of AlN thin layers, grown in a hybrid helicon-arc ion-plasma reactor, to enhance significantly heat dissipation from crystalline he...

Spin-dependent ballistic transport in a mesoscopic three-terminal Y-shaped setup with a spin-discriminating ferromagnetic membrane in one of the outgoing leads is studied using the Landauer–Büttiker formalism. Our calculations, performed at sufficiently low temperatures when thermal effects and magnon scattering become vanishingly small, predict a...

Quantum entanglement is among the main fundamental resources for quantum information processing tasks like quantum communication, quantum computation, etc. The states with such kind of a nonlocal correlation can easily be obtained from a single-mode wave packet using a passive linear beam splitter. Taking into account scalable arguments and thus th...

Penetration of spin-polarized charges from a nearby ferromagnetic metallic layer into 100-μm-wide superconducting films of Pb and Mo–Re alloy with similar critical parameters but quite different spin-orbit coupling strengths is studied. It is shown that the diffusion of magnetic properties into a nearby superconductor can be employed as an electric...

A novel self-textured nanofilament technique based on the resistive-switching effect in nano-scale transition-metal oxide films has been developed. While traditional tunneling and point-contact approaches to the electron–boson interaction spectroscopy in a strong-coupled superconductor are realized on different samples, the novel method allows one...

The efficiency of aluminum nitride films as thermal interfaces has been studied. It is shown that such films obtained in a hybrid helicon-arc ion-plasma reactor significantly improve the heat removal from the crystals of electronic devices, in particular, from powerful LEDs or LED assemblies, and thus noteworthy increase their luminosity, reliabili...

Thin-film hybrid heterostructures formed by superconducting molybdenum-rhenium-alloy films with a critical temperature of about 9 K and nanoscale silicon-based semiconducting interlayers with metallic tungsten nanorods have been fabricated and studied. Current-voltage characteristics of the junctions were measured at 4.2 K and under influence of 11...

We present a proof-of-concept nanoelectronics device with a negative differential conductance, an attractive from the applied viewpoint functionality. The device, characterized by the decreasing current with increasing voltage in a certain voltage region above a threshold bias of about several hundred millivolts, consists of two superconducting ele...

Using simplified models, we have demonstrated how a single-electron wave packet can be engineered to realize directional and controlled transfer of quantum information across superconducting networks. A scheme to design different (energetically allowed) outcomes by tuning a single characteristic parameter of the driven pulse is proposed. We have id...

Effect of the thickness of a nanoscale layer of fer-romagnetic nickel in direct contact with a supercon-ductor on the density of quasiparticle states of a lead film, a conventional superconductor with singlet pair-ing of electrons, has been studied (reverse proximity effect). It was found that the penetration depth of su-perconducting correlations...

The Braess paradox encountered in classical networks is a counterintuitive phenomenon when the flow in a road network can be impeded by adding a new road or, more generally, the overall net performance can degrade after addition of an extra available choice. In this work, we discuss the possibility of a similar effect in a phase-coherent quantum tr...

The trend towards miniaturization of electronic devices and simultaneous increase of microelectronics packaging density results in a large amount of heat generated during their operation. To reduce the thermal contact resistance between a silicon chip, the heat source and a substrate of integrated circuits, the heat sink is one of the main tasks at...

Conventional Josephson metal-insulator-metal devices are inherently underdamped and exhibit hysteretic current-voltage response due to a very high subgap resistance compared to that in the normal state. At the same time, overdamped junctions with single-valued characteristics are needed for most superconducting digital applications. The usual way t...

Emergence of phase-slip lines is one of the main mechanisms for dissipation in current-carrying superconducting thin films with lateral dimensions larger than the superconducting coherence length. We show that effective control of the wide resistive region between dissipation-free and completely ohmic transport regime can be achieved by evaporating...

Josephson-junction devices such as suitably designed nanoSQUIDs can provide a sensing element for micro- and nanoelectronics. In this context, the properties of such device must be tailored in order to have an optimal response. In particular, it relates its temperature stability, and a comparatively weak dependence of the critical supercurrent Ic o...

Physical nature of hysteretic transport characteristics of two solid-state structures is discussed. For heterocontacts formed by a metal counter electrode with a complex transition-metal oxide, it is shown that two-valued current - voltage dependences appear due to the migration of the O vacancies under the influence of an external electric field w...

Quantitative description of charge transport across tunneling and break-junction devices with novel superconductors encounters some problems not present or not as severe for traditional superconducting materials. In this work, we explain unexpected features in related transport characteristics as an effect of a degraded nanoscaled sheath at the sup...

We have studied a bipolar resistive switching phenomenon in c-axis oriented normal-state YBa2Cu3O7- c (YBCO) thin films at room temperature by scanning spreading resistance microscopy (SSRM) and scanning tunneling microscopy (STM) techniques. The most striking experimental finding has been the opposite (in contrast to the previous room and low-temp...

Possible origin of the anomalous structure "peakdip-hump" in tunneling characteristics of hightemperature superconductors with a degraded nearsurface layer is analyzed. The discussed feature is composed of two peaks in the energy-gap vicinity separated by a region of suppressed conductance. One of them is usually high and sharp whereas the second o...

The possibility of an anomalous structure in the differential conductivity of tunnel junctions based on high-temperature superconductors as a result of degradation of their surface layer is analyzed. This feature is in the form of two peaks near an energy gap separated by a region of suppressed conductivity. One peak is usually high and sharp, whil...

An overview of the superconducting proximity effect.

Thin film heterostructures composed of superconducting electrodes (molybdenum rhenium alloy) and a nanoscale silicon layer doped with tungsten, have been designed and experimentally studied. The current-voltage characteristics of junctions exhibiting local maxima of the current against the background of abrupt current increases for the first time,...

Following the ever-rising demand for new functionalities and novel materials in superconducting circuitry, we provide a complete view on the self-shunting problem in Josephson junctions, relating it to specific features of a multichannel weak link between electrodes where averaging over the channels yields a bimodal distribution of transparencies w...

We discuss the use of polymer films as infrared-radiation filters. Numerical calculations of thermal characteristics of polymer films placed on a section of a circular waveguide are performed. It is shown that an additional coverage of such films with a layer with a high thermal-conductivity coeffi- cient is needed for the realization of effective...

Thermally activated topological defects of the superconducting condensate are the primary source of dissipation in mesoscopic two-dimensional superconducting structures. We propose a new approach for analyzing the resistivity mechanism in such systems by suppressing local superconducting properties with spin-polarization injection. Applying externa...

We present experimental results relating both the fabrication and characterization of superconducting hybrid S-F-I-S junctions that employ molybdenum-rhenium alloy as one of the superconducting electrodes, Ni2MnGa compound as a ferromagnetic interlayer, oxidized Ni2MnGa as an insulator, and superconducting Pb/Sn bilayer as the counter-electrode. Un...

ResultsofthemeasurementsofthetemperatureandfielddependencesofthemagneticmomentoftheSi—TiN—FeandSi—TiN—Fe/Cheterostructureswithironnanoclustersinmagneticfieldsdirectedparallelandperpendicularlytothesubstrateplanearepresented.Inthetemperaturerangefrom5to300K,asuperparamagneticbehaviourofthesusceptibilityofasystemwithasuffi-cientlystronganisotropyisob...

Submicron Josephson devices are of a particular interest to the emerging field of quantum information, nanosized superconducting quantum interference devices (nano-SQUID) fabrication, AC voltage synthesis circuits for quantum metrology, etc. In this paper, we report on the development of our technology for producing non-hysteretic Nb/Al-AlOx-Nb fou...

We have studied transport characteristics of mesoscopic multiple-mode superconducting contacts formed be- tween two grains in bulk two-gap magnesium diboride. The experimental setup was realized by driving a nor- mal-metal tip into MgB2 polycrystalline sample and proved to be extremely stable, providing possibility to perform pressure experiments a...

This chapter shows that the main ingredient of the superconducting state is that electron pairs form a macroscopic matter wave. The well-defined phase of the matter wave leads to the ideal diamagnetism at not too large fields and to the vortex state in type-II superconductors. The chapter introduces important length scales like the London penetrati...

We have fabricated trilayered sandwiches consisting of superconducting electrodes made of MoRe alloy with a critical temperature of about 10 K and a silicon interlayer of thicknesses up to 20 nm doped by tungsten with atomic concentrations up to 10 at%. For concentrations below 5 at%, measurements of transport characteristics have revealed the pres...

Theoretical and experimental analysis of electron transport across ultrathin, homogeneously disordered oxide layers is presented with particular regard to the question of how much the effects are universal. We show that (i) distribution of transparencies across dirty subnanometer-thick insulating films is bimodal and (ii) conductance-voltage charac...

Current-voltage characteristics of fabricated MoRe-Si (W)-MoRe heterojunctions are investigated in a wide range of changes in the parameters (such as thickness and dopant concentration) of the semiconductor Si (W) barriers. As found, at relatively high concentrations (5-9 at.%) of tungsten in the silicon barriers, a resonant tunnelling effect occur...

Conductivity of current-biased La0.82 Ca0.18 MnO3 low-doped manganite single crystals has been investigated in wide temperature and magnetic field ranges. Strong zero-bias anomalies in the form of conductance minima and maxima have been observed below the Curie temperature TC. Applied magnetic field and temperature strongly affect the anomaly and c...

Despite a long history, the two-band/two-gap theory of superconductivity (S) had no important implications in the last century. The first specific but representative case was MgB2, a comparatively simple compound with an unexpectedly high normal-to-superconductor transition temperature Tc = 39 K. Superconductivity in MgB2 resides in two distinct gr...

The increasing interest in charge transport across amorphous nanometer-thick oxide layers is motivated by their promising applications in semiconductor and superconductor electronics. But usually, electrical characteristics of corresponding devices strongly differ from those following from a conventional theory of tunneling processes. In this work...

An interesting feature of Superconductor–Normal metal–Superconductor Josephson junctions for digital applications is due to their non-hysteretic current–voltage characteristics in a broad temperature range below Tc. This allows to design Single-Flux-Quantum (SFQ) cells without the need of external shunts. Two advantages can be drawn from this prope...

The simulation of charge transport in Josephson junctions through inhomogeneous nanolayer insulator films is performed, and tunnelling characteristics of the superconducting junctions on the base of two-band superconductors are theoretically estimated at near zero bias voltage. Charge transport is considered as a movement of the Bogolyubov quasi-el...

We discuss an universal effect in tunnel characteristics of layered metal - insulator – metal structures, where the dielectric barrier is formed by a nanoscale disordered oxide film: a universal distribution of the insulator layer transparencies, which does not depend on specific microscopic characteristics of it. Experimental results for supercond...

Device-modeling physics of four-layered Nb/Al-ultra-thin AlOx barrier-Nb Josephson structures is discussed, emphasizing practical applications. The temperature effect on the minigap induced in a proximized Al layer and that on a critical voltage across the SNIS junction is numerically simulated. The McCumber-Stewart parameter is found to decrease f...

Conductivity noise in dc current biased La_{0.82}Ca_{0.18}MnO_{3} single crystals has been investigated in different metastable resistivity states enforced by applying voltage pulses to the sample at low temperatures. Noise measured in all investigated resistivity states is of 1/f-type and its intensity at high temperatures and low dc bias scales a...

Two possible mechanisms for the partial or complete loss of information contained in the quantum-mechanical phase of an electron moving in a stochastic solid-state structure are examined. The first involves phase randomization of the electron characteristics (for example, by elastic scattering of electrons on defects in thin metallic layers) and th...

Resistance switching effects in metal/perovskite contacts based on epitaxial c-axis oriented YBa2Cu3O6+c (YBCO) thin films with different crystallographic orientation have been studied. Three types of Ag/YBCO junctions with the contact restricted to (i) c-axis direction, (ii) ab-plane direction, and (iii) both were designed and fabricated, and thei...

We report low-temperature measurements of current–voltage characteristics for highly conductive Nb/Al–AlOx–Nb junctions with thicknesses of the Al interlayer ranging from 40 to 150 nm and ultrathin barriers formed by diffusive oxidation of the Al surface. In a superconducting state these devices have revealed a strong subgap current leakage. Analyz...

A new general approach to calculations of the tunneling characteristics of heterostructures involving nanodimensional disordered insulating films has been developed with allowance for both elastic and inelastic electron tunneling. It is shown that, by determining the value of the exponent in the dependence of the differential conductivity of these...

We report on our recent electron-tunneling studies of bulk manganite samples that provide important information about the structure of the near-surface layers of the material and the nature of the charge transport across them. It is shown that the even part of the differential conductance of contacts formed by a metallic injector with the surface o...

Tunneling and resistive measurements have been performed on high-Tc YBCO thin films. Both the effects of electron-electron correlations and those of electron-phonon interactions are found and discussed.

We report on tunneling and Andreev-reflection conductance spectra of 39 K superconducting magnesium diboride, obtained with Pb and Au counter-electrodes. Two distinct steps at close to 2.7 and 7.1 meV appear in a low-resistance metallic-type Au–MgB2 junction characteristic, whereas a tunneling-like spectrum measured for the same junction, annealed...

The observation of an anomalous temperature behavior of the differential conductance versus voltage curves in contacts formed by an Ag tip and a bulk ceramic LaBa2Cu3O7-x with Tc around 92 K is reported. For a wide range of temperatures from Tc to helium-liquid ones, we have found a crossover from curves typical for a pure conducting normal metal–s...

Strong differential resistance peaks have been observed in the point-contact characteristics of normal state copper-oxide ceramics. A possible interpretation of the spikes that have been found previously for a variety of high-Tc superconducting polycrystalline samples is discussed.

Motivated by a recent experiment evidencing an unusual double-peak structure in tunneling conductance spectra of a nano-sized ferromagnet- superconductor bilayer, we propose a clean-limit scattering-like model for a quasi-ballistic transport in superconducting heterostructures with conducting ferromagnetic films. The model also includes an effect o...

Josephson junctions with non-hysteretic current-voltage characteristics form the basis of most superconducting electronic circuits including RSFQ logic and programmable Josephson voltage standards. In contrast to conventional SIS devices, Nb/Al-AlO_x-Nb (SNIS) junctions with an additional comparatively thick Al interlayer and a comparativ...

Low frequency noise in current biased La0.82Ca0.18MnO3 single crystals has been investigated in a wide temperature range from 79 to 290 K. Despite pronounced changes in the magnetic properties and dissipation mechanisms of the sample with changing temperature, the noise spectra were found to be always of the 1/f type, and their intensity (except fo...

Low frequency noise in current biased La$_{0.82}$Ca$_{0.18}$MnO$_{3}$ single crystals has been investigated in a wide temperature range from 79 K to 290 K. Despite pronounced changes in magnetic properties and dissipation mechanisms of the sample with changing temperature, the noise spectra were found to be always of the 1/f type and their intensit...

We demonstrate theoretically and experimentally that a ferromagnetic layer as thin as a few nanometres, which is almost transparent for non-superconducting charge transport, can be used as a cut-off filter to block transport of charge-carrier superconducting correlations. This property may be exploited in some applications, as is exemplified by the...

The measurements of dc Josephson and quasiparticle current-voltage characteristics of four-layered Nb / Al – AlO _x– Nb devices with a fixed Nb thickness of 270 nm and Al thicknesses ranging from 40 to 120 nm are reported and analyzed in the framework of a microscopic model developed to determine stationary properties of dirty limit doubl...

Perspective Josephson Mo-Re alloy-oxide-Pb, MgB2- oxide – Mo-Re alloy and Mo-Re alloy-normal metal-oxide- normal metal-Mo-Re alloy junctions have been fabricated and investigated. Thin (~50-100 nm) MoRe superconducting films are deposited on Al2O3 substrates by using a dc magnetron sputtering of MoRe target. Thin (~50-100 nm) MgB2 superconducting f...

Motivated by a search for a suitable technology to fabricate Josephson junctions with a tunable damping regime, we performed a systematic study of the temperature effect on the critical current in Nb/Al-AlOx-Nb heterostructures with a nanometer-thick Al interlayer. For Al layer thicknesses ranging from 40 to 110 nm, we have observed a transition fr...

Current-voltage characteristics of planar junctions formed by an epitaxial c-axis oriented YBa2Cu3O7-x thin film micro-bridge and Ag counter-electrode were measured in the temperature range from 4.2 K to 300 K. A hysteretic behavior related to switching of the junction resistance from a high-resistive to a low-resistive state and vice-versa was obs...

The effect of the top of the valence band of an insulator on spin filtering in tunnel structures with nanometer magnetic dielectric layers is discussed. It has been shown that the effect disappears completely at a zero bias voltage and is significantly suppressed at finite voltages if the Fermi level lies in the middle of the band gap of the insula...

Giant growth of the differential resistance has been observed in a tunnel junction consisting of superconducting lead with Heusler's ferromagnetic alloy Co2CrAl for low bias voltages. This effect is attributed to the appearance of a nonequilibrium state in the lead film as a result of spin injection into the superconductor.

The paper gives a short overview of electronic characteristics of ZrB12 single crystals in normal and superconducting states. First-principles calculations of the electronic structure and charge density redistribution reveal that zirconium dodecaboride belongs to the class of ‘covalent metals’ with itinerant electronic states at the Fermi energy co...