High-temperature Superconductor YBa2Cu3O7 Research Articles

A flux-tunable YBa2Cu3O7 quantum interference microwave circuit

Josephson microwave circuits are essential for the currently flourishing research on superconducting technologies, such as quantum computation, quantum sensing, and microwave signal processing. To increase the possible parameter space for device operation with respect to the current standards, many materials for superconducting circuits are under active investigation. Here, we present the realization of a frequency-tunable, weakly nonlinear Josephson microwave circuit made of the high-temperature cuprate superconductor YBa2Cu3O7 (YBCO), a material with a high critical temperature and a very high critical magnetic field. An in situ frequency-tunability of ∼300 MHz is achieved by integrating a superconducting quantum interference device (SQUID) into the circuit based on Josephson junctions directly written with a helium ion microscope (HIM). Our results demonstrate that YBCO-HIM-SQUID microwave resonators are promising candidates for quantum sensing and microwave technology applications.

Properties of percolation channels in planar memristive structures base on epitaxial films of oxide perovskite compounds YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7 – δ</sub> and La<sub>1 – <i>x</i></sub>Sr<sub><i>x</i></sub>MnO<sub>3 – δ</sub>

The choice of base materials and the use of their functional properties in the development of the structure and elucidation of the mechanism of resistive switching has been analyzed. Mesoscopic heterostructures based on epitaxial oriented 〈001〉 films of high-temperature superconductor YBa2Cu3O7 – δ and doped manganite La1 – xSrxMnO3 – δ, were obtained, and the properties of percolation channels of structures based on these compounds were studied. The effects of “self-adapting electroforming” in microcontact heterostructures based on epitaxial films of manganite are observed. Numerical calculations using the critical electric field model have shown that “self-electroforming” occurs in strong electric fields and a gap structure is formed in the contact zone. This structure provides reproducibility of resistive switching.

Improvement of microwave characteristics for high-T c superconductor (YBCO) films by ion irradiation treatment

Measurements of the microwave surface impedance for high-temperature superconductor YBa2Cu3O7−x (YBCO) films irradiated by 3 MeV Au2+ ions at three irradiation doses (1010 cm−2, 1011 cm−2, and 1012 cm−2) were carried out at different temperatures (below the critical temperature of T с ≈ 90 К) and various rf current amplitudes by the use of the microstrip resonator technique. A noticeable decrease in the surface resistance and an enhancement of the linear response range at low temperatures were observed for moderately irradiated film exposed to an irradiation dose of 1011 cm−2, while at higher irradiation doses (1012 cm−2) an increase in the surface resistance and a decrease in the linear response range were observed for all temperatures below T c. These results are discussed in the framework of phenomenological theory for the microwave response of superconductors with nano-sized structural defects.

Meissner effect and structural inhomogeneity in HTSC YBa-=SUB=-2-=/SUB=-Cu-=SUB=-3-=/SUB=-O-=SUB=-6.92-=/SUB=-

For optimally doped high-temperature superconductors YBa2Cu3O6.92 with various degrees of structural inhomogeneity, the influence of this inhomogeneity on the manifestation of the Meissner effect is considered. The measurement results indicate that for the samples under study, for which almost identical superconducting transition Tc~92 K temperatures were realized, the Meissner effect values turned out to be different and correlated with the degree of structural inhomogeneity, which is also characteristic of other magnetic properties. Keywords: Superconductivity, HTSC, structural disorder, magnetic properties, d-wave nodes, Fermi arcs, Meissner effect.

Эффект Мейсснера и структурная неоднородность в ВТСП YBa-=SUB=-2-=/SUB=-Cu-=SUB=-3-=/SUB=-O-=SUB=-6.92-=/SUB=-

For optimally doped high-temperature superconductors YBa2Cu3O6.92 with various degrees of structural inhomogeneity, the influence of this inhomogeneity on the manifestation of the Meissner effect is considered. The measurement results indicate that for the samples under study, for which almost identical superconducting transition Tс = 92K temperatures were realized, the Meissner effect values turned out to be different and correlated with the degree of structural inhomogeneity, which is also characteristic of other magnetic properties.

Normal-state charge transport in YBa2Cu3O6.67 under uniaxial stress

To provide a foundation for theoretical models of high-temperature superconductivity, experimental research has sought to establish correspondences between macroscopic transport coefficients on the one hand, and atomic-scale correlation functions measured by spectroscopic and scattering probes on the other hand. This research avenue has been confounded by the gradual onset of electronic ordering phenomena and of the corresponding transport anomalies. We report measurements of the uniaxial-stress dependence of the normal-state resistivity and Hall coefficient of the underdoped high-temperature superconductor YBa2Cu3O6.67. We observe a remarkable correspondence between the differential stress responses of the transport coefficients and resonant X-ray diffraction features indicative of charge ordering, which parallels the phenomenology of classical charge-density-wave compounds. However, our observations imply that static charge order is not responsible for a sign reversal of the Hall coefficient, and suggest that the interplay with liquid-like, dynamical charge correlations is essential for the prominent transport anomalies in the underdoped cuprates.

Effect of Graphene Nanoparticles Addition on Superconductivity of YBa2Cu3O7~δ Synthesized via the Thermal Treatment Method

The development of high-temperature superconductor (HTS) YBa2Cu3O7~δ (Y123) bulks in industrial applications were established years ago. It is one of the developments that currently attracts great attention especially in transportation, superconductor cables and wires. This study is focused on the preparation of the Y123 bulk superconductors by the thermal treatment method due to the promising ways to develop high-quality Y123 superconductors with its simplicity, low cost, and relatively low reaction temperature used during the process. Y123 were added with graphene nanoparticles (x = (0.0–1.0) wt.%). Samples were then characterized by X-ray diffraction (XRD) analysis, field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), and alternating current susceptibility (ACS). It was found that Y123 confirmed that the majority of phases in all the XRD patterns was the orthorhombic crystal structure and the Pmmm space group with secondary phases belonged to Y2Ba1Cu1O5 (Y211). The highest Tc obtained when graphene nanoparticles were added in the Y123 sample was x = 1.0 wt.%, followed by x = 0.5 wt.% with 92.64 and 92.59 K, respectively. From the microstructure analysis, the average grain size significantly decreased to 4.754 µm at x = 0.5 wt.%. The addition of graphene nanoparticles had disturbed the grain growth of Y123, affecting the superconducting properties of the samples. On the other hand, the intergranular critical current density, Jcm, was found to increase with graphene nanoparticle addition and had the highest value at x = 1.0 wt.%, indicating that graphene nanoparticles acted as pinning centers in the Y123 matrix.

Capture of magnetic flux in high-temperature superconductor YBa2Cu3O7 and its destruction

Capture of magnetic flux in high-temperature superconductor YBa2Cu3O7 and its destruction

Synthesis of porous high-temperature superconductors via a melamine formaldehyde sacrificial template.

Nanostructured high-temperature superconductors YBa2Cu3O6+δ and Bi2Sr2CaCu2O8+δ were synthesised using a melamine formaldehyde sponge as a sacrificial template, via three solution-based approaches. In the case of YBa2Cu3O6+δ, a modified Pechini method produced a material with a superconducting transition at 92 K and a specific surface area of 4.22 m2 g−1. Further analysis with Hg porosimetry determined that the sponge exhibited a porosity of 82%. In the case of Bi2Sr2CaCu2O8+δ, this method produced a material that exhibited superconductivity at 86 K with a specific surface area of 9.62 m2 g−1. Hg-porosimetry determined that the BSCCO sponge exhibited a porosity of 78%.

Magnetoresistance investigation in the mixed state of a high temperature superconductor

In this work, we analyze the behavior of the magnetoresistance R (H, T) of a high temperature superconductor YBa 2 Cu 3 O 7−δ thin film optimally doped. Measurements of the magnetoresistance were carried out in the mixed state for a magnetic field up to 14 T applied parallel to c − axis then parallel to ab − plane with a dc transport current of 100 and 500 nA, 0.1 and 0.3 mA perpendicular to the magnetic field direction in both cases. The obtained results show that the magnetoresistance is in a good agreement with the thermally assisted flux creep. However, the magnetoresistance in the flux flow regime cannot be described by the Barden-Stephen model which conjectures another origin of these results. In this sense, the quantum fluctuations of the order parameter is a good alternative to understanding the shape of the magnetoresistance. The comparison of the magnetoresistance of the two directions shows that [see formula in PDF] is larger than [see formula in PDF] with anisotropy factor [see formula in PDF] depending on temperature and magnetic field. The irreversibility line H irr (T) as well as H C2 (T) are determined and the first one is fitted with the phenomenological model H irr (T) = H irr (0) (1 − T/T o ) α where H irr (0), T o and α are parameters obtained from the fit. The investigation of the scaling law allows us to prove that a crossover from 3D to 2D behavior is a feature of our sample which justifies the existence of the decoherence effect.

Complexes of Parallel Grain Boundaries in YBa2Cu3O7 Film for Josephson Junction Chains and Arrays

Substrates consisting of five parallel planar grain boundaries (GBs), oriented perpendicular to the surface and spaced by several micrometers, have been grown by solid-phase bonding of fianite crystals in order to obtain large complexes of closely spaced bicrystal Josephson junctions based on high-temperature superconductor (HTSC) films. The substrates had a crystallographic orientation (100) and dimensions of 1.0 × 10.0 × 10.0 mm3. All GBs were of symmetrical type, and their lattices were rotated by 12° in opposite directions around the axis perpendicular to the surface. The distance between GBs in a packet complex was 15 µm, and this value was maintained with an error of no more than 1 µm along their entire length of 10 mm. The deviation of the shape of all five GBs from an ideal geometric plane was within 1 µm along their entire length. Films of HTSC YBa2Cu3O7 with inheritance of GBs were grown on these substrates. Structures of two types were formed on the films using lithography. It is shown that the use of these fianite substrates in HTSC-based devices of cryogenic electronics increases significantly the density of bicrystal Josephson junctions; reduces several times the total length of superconducting lines connecting these junctions; and, correspondingly, decreases significantly the inductive resistance of these circuits and improves their electrical characteristics in comparison with the structures having similar functions but based on one or two parallel GBs.

The Study of Switching Dynamics in Planar Structures Based on Epitaxial Films of YBa2Cu3O7-δ High-Temperature Superconductor

We have been studying the dynamic effects of bipolar resistive switching (BERS) in memristive planar heterostructures based on c-oriented epitaxial films of the high-temperature superconductor YBa2Cu3O7 (YBCO). We have been observing the suppression of the memristive properties of the structures under sinusoidal and pulse loads and the nucleation and the evolution of the regions of current density and electric field in the structures under study. We found that the limiting frequencies of a sinusoidal type load for observing the switching effect are frequencies of about 104 Hz. It has been shown that the percolation channel is formed by the appearance of electric field domains in which the electric field threshold is reached. The switchings are controlled by two processes, with time t < ms and a longer time of the order of a few seconds. Possible physical models of the observed phenomena are being discussed.

Experimental and theoretical Raman study on the HTSC [formula omitted] family for different Pr concentrations and synthesis methods

We present a joint study of confocal Raman spectroscopy, supported by the oretical simulations, together with resistivity and X-ray diffraction measurements on the high temperature superconductor (HTSC) YBa2Cu3O7 family doped with Pr atoms. The samples are grown using two different synthesis routes: sol–gel and solid-state reaction. Samples produced by both methods present similar structural and morphological properties but small differences are observed in their superconductive properties and vibrational response. The latter is correlated with ab-initio simulations for different concentrations of Pr. We find that as the Pr concentration increases, the presence of a forbidden B1u mode is enhanced. This is explained by a loss of the centrosymmetric symmetry when Pr is present. The different effects in the Raman modes with Pr content are explained by the change of interatomic distances in the inner cell. Finally, the good correlation obtained between experimental Raman spectra and ab-intio calculations validated the latter, allowing to study the evolution of the electronic band structure as a function of Pr content and ionic radii. Once again, we explained the difference observed by the changes in the atoms distribution inside the unit cell.

The Berezinskii–Kosterlitz–Thouless topological phase transition in the Josephson medium of granular high-temperature superconductors under the effect of magnetic and electric fields

This study establishes the identity of the topological phases that emerge in the Josephson medium of granular high-temperature superconductors YBa2Cu3O7–δ in the process of the Berezinskii–Kosterlitz–Thouless (BKT) phase transitions, under the influence of an external magnetic field and transport current. The nature of the topological phases arising as a result of the BKT phase transition was found to be independent of the type of external effect.

Spatially inhomogeneous competition between superconductivity and the charge density wave in YBa2Cu3O6.67

The charge density wave in the high-temperature superconductor YBa2Cu3O7−x (YBCO) has two different ordering tendencies differentiated by their c-axis correlations. These correspond to ferro- (F-CDW) and antiferro- (AF-CDW) couplings between CDWs in neighbouring CuO2 bilayers. This discovery has prompted several fundamental questions: how does superconductivity adjust to two competing orders and are either of these orders responsible for the electronic reconstruction? Here we use x-ray diffraction to study YBa2Cu3O6.67 as a function of magnetic field and temperature. We show that regions with F-CDW correlations suppress superconductivity more strongly than those with AF-CDW correlations. This implies that an inhomogeneous superconducting state exists, in which some regions show a fragile form of superconductivity. By comparison of F-CDW and AF-CDW correlation lengths, it is concluded that F-CDW ordering is sufficiently long-range to modify the electronic structure. Our study thus suggests that F-CDW correlations impact both the superconducting and normal state properties of YBCO.

The role of kinetic inductance on the performance of YBCO SQUID magnetometers

Inductance is a key parameter when optimizing the performance of superconducting quantum interference device (SQUID) magnetometers made from the high temperature superconductor YBa2Cu3O7−x (YBCO) because lower SQUID inductance L leads to lower flux noise, but also weaker coupling to the pickup loop. In order to optimize the SQUID design, we combine inductance simulations and measurements to extract the different inductance contributions, and measure the dependence of the transfer function VΦ and flux noise on L. A comparison between two samples shows that the kinetic inductance contribution varies strongly with film quality, hence making inductance measurements a crucial part of the SQUID characterization. Thanks to the improved estimation of the kinetic inductance contribution, previously found discrepancies between theoretical estimates and measured values of VΦ and could to a large extent be avoided. We then use the measurements and improved theoretical estimations to optimize the SQUID geometry and reach a noise level of = 44 fT/ for the best SQUID magnetometer with a 8.6 mm × 9.2 mm directly coupled pickup loop. Lastly, we demonstrate a method for reliable one-time sensor calibration that is constant in a temperature range of several kelvin despite the presence of temperature dependent coupling contributions, such as the kinetic inductance. The found variability of the kinetic inductance contribution has implications not only for the design of YBCO SQUID magnetometers, but for all narrow linewidth SQUID-based devices operated close to their critical temperature.

Mathematical modeling of current-voltage characteristics of high-temperature superconductors with fractal boundaries of normal phase clusters

The fractality effect of the normal phase clusters' boundaries of a high-temperature superconductor YBa2Cu3O7−x (YBCO) on the magnetic flux creep is investigated. Experimental current-voltage and magnetoresistive characteristics of YBCO at the boiling point of nitrogen are obtained. Based on the model of intergranular clusters with fractal boundaries, an approximation of the experimental data is obtained after geometric-probability analysis of the photomicrographs of the samples. A model of the magnetoresistive state caused by flux creep is proposed for various transport currents, and experimental and empirical dependences of the fractal dimension of the normal YBCO phase cluster boundaries on the constant magnetic field are found. The magnetic field intensity is determined for a given fractal dimension, at which the vortex penetration into the granules begins. It is shown that the state of the samples corresponds to the metastable phase of the vortex glass. The connectivity index of the stall paths of the vortex bundles at the percolation threshold is calculated.

Series arrays of planar long Josephson junctions for high dynamic range magnetic flux detection

We investigated series arrays of closely spaced, planar long Josephson junctions for magnetic field transduction in Earth’s field, with a linear response and high dynamic range. The devices were fabricated from thin film high-temperature superconductor YBa2Cu3O7−δ (YBCO) thin films, using focused helium ion beam irradiation to create the Josephson barriers. Four series arrays, each consisting of several hundreds of long junctions, were fabricated and electrically tested. From fits of the current-voltage characteristics, we estimate the standard deviation in critical current to be around 25%. Voltage-magnetic field measurements exhibit a transfer function of 42 mV/mT and a linear response over a range of 303 μT at 71 K, resulting in a dynamic range of 124 dB.

Thermodynamic Properties of Stoichiometric Non-Superconducting Phase Y2BaCuO5.

Y2BaCuO5 often occurs as an accompanying phase of the well-known high-temperature superconductor YBa2Cu3O7 (also known as YBCO). Y2BaCuO5, easily identifiable due to its characteristic green coloration, is often referred to as ‘green phase’ or ‘Y-211’. In this contribution, Y2BaCuO5 phase was studied in detail with a focus on its thermal and thermodynamic properties. Energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were employed in the study of sample’s morphology and chemical composition. XRD data were further analyzed and lattice parameters refined by Rietveld analysis. Simultaneous thermal analysis was employed to study thermal stability. Particle size distribution was analyzed by laser diffraction. Finally, thermodynamic properties, namely heat capacity and relative enthalpy, were measured by drop calorimetry, differential scanning calorimetry (DSC), and physical properties measurement system (PPMS). Enthalpy of formation was assessed from ab-initio DFT calculations.

Growth and Nanofabrication of All-Perovskite Superconducting/Ferromagnetic/Superconducting Junctions

We fabricate and study experimentally all-perovskite-oxide superconductor/ferromagnetic insulator/superconductor (S/FI/S) tunnel junctions made out of the high-temperature cuprate superconductor YBa2Cu3O7−y (YBCO) and the colossal magnetoresistive manganite LaMnO3 (LMO) in the ferromagnetic insulator state. YBCO/LMO/YBCO heterostructures with different LMO thicknesses (5, 10, and 20 nm) are grown epitaxially via pulsed laser deposition. Nanoscale S/FI/S junctions with sizes down to 300 nm are made by three-dimensional nano-sculpturing with focused ion beam. Junctions with a thick (20 nm) LMO barrier exhibit a large negative magnetoresistance below {T}_{Curie}sim 160 K, typical for colossal magnetoresistive manganites, as well as a kink in the current-voltage characteristics at large bias ( Vsim 1 –2 Volts), attributed to Zener-type tunneling. However, they do not show a measurable Josephson current. On the contrary, junctions with the thinnest 5-nm LMO barrier exhibit a large supercurrent and no signs of magnetism. The latter may indicate the presence of pinholes due to thickness inhomogeneity and/or a sim 2 nm dead magnetic layer at the YBCO / LMO interface caused, e.g., by interdiffusion or strain. The junction with an intermediate 10-nm LMO barrier exhibited a desired S/FI/S junction behavior with significant negative magnetoresistance and signatures of a small Josephson current.