high-Tc Superconductors Materials Research Articles

Prediction of the resistivity of YBa2Cu3O7-δ superconductor by a highly sensitive one-dimensional phononic crystal sensor

In this research, we have theoretically introduced a new application of one-dimensional (1D) phononic crystals (PnCs) manifested as a sensor for the variations in porosity ratios of a high Tc superconductor material (Ba2Cu3O7-δ). Notably, there is a massive need for accurate detection of the changes in the porosity ratio of the YBa2Cu3O7-δ material due to the dependence of its resistivity and critical current density Jc as well on the porosity ratio. Meanwhile, the changes in the porosity ratio could be demonstrated by tuning a resonant mode in the transmission spectrum of the 1D PnC. Therefore, we considered the YBa2Cu3O7-δ as a defect layer inside the periodic design (Lead/Epoxy)N of the 1D PnC. Herein, the transfer matrix method (TMM) is used to calculate the transmission spectra of the proposed design. Our findings showed that the proposed sensor is capable of detecting and sensing the variations in the porosity ratio of YBa2Cu3O7-δ as well as indicating its mechanical properties with relatively high performance and sensitivity. Moreover, the obtained results have unfolded a very sensitive effect in the resonant peak position based on the physical properties of YBa2Cu3O7-δ. Since the position of the resonant peak is highly sensitive to the smallest changes in the porosity ratio. Finally, the investigated sensitivity and quality factor can reach the values of 75.04 kHz and 186.474, respectively, for a 1% change in the porosity of YBa2Cu3O7-δ. In a nutshell, it's a new way of correlating the mechanical properties of a porous high Tc superconducting material based on the porosity ratio that may be used in various industrial and technological applications.

High-Tc Superconducting Microwave and Millimeter Devices and Circuits—An Overview

High temperature (high-Tc) superconductors (HTS) have found many applications in the last two decades. To microwave researchers and engineers, the ultra-low surface resistance of the thin-film HTS materials at microwave and millimeter frequencies and the highly non-linear Josephson junctions are of particular interest. The former can be exploited in the design and fabrication of passive microwave components and circuits with superior performance, and the latter can be exploited to create many novel active HTS devices. This paper provides an overview of the state-of-art development of HTS devices and circuits for microwave and mm-wave communication front-end receiver systems. The paper is particularly focused on the latest advancement of HTS Josephson junction based active devices, monolithic microwave integrated circuits (MMIC), and whole receiver systems integrated with cryocoolers.

The Optical Properties of Metamaterial-Superconductor Photonic Band Gap With/Without Defect Layer

In the present work, we have investigated theoretically the optical properties of a new one-dimensional defected photonic crystal structure (1DDPC). The structure is composed of alternating layers of metamaterial (double-negative material) and high Tc superconductor material called Hg1223 defected with a dielectric material (SiO2) at the center of the structure. The transmittance spectra of the proposed structure are obtained by using the transfer matrix method (TMM). We noticed that multiple transmittance peaks within the photonic band gap (PBG) as the thickness of defect layer increases. The tunable filtering feature is obtained by varying the thicknesses of metamaterial and superconductor layer. In addition, the defect peak is red shifted as well as photonic band gap tuned to low-frequency region. Our structure is sensitive to the variation of the angle incidence. Also, defect mode shown to be blue shifted as the angle of incidence increases. The tunable filtering properties are very useful in the optoelectronic applications.

New micro-magnetometer device is made from high-temperature superconductor

A superconducting quantum interference device, using a high-Tc superconductor material, can be fashioned into a small magnetometer with high field sensitivity and low noise.

(Keynote) Oxide Semiconductors, Solid-State Chemistry, and Photoelectrochemistry: A Nexus

Solid-state chemistry languished as an esoteric discipline till interest exploded on the so-called high-Tc superconductor materials; oxides were discovered to have unique properties in this regard. Paralleling this was the gradual realization that solid-state chemistry principles underpinned many technologically-important areas such as batteries, supercapacitors, and even solar cells. The culmination of this trend was in the application of solid-state chemistry to the preparation and characterization of electrode materials in photoelectrochemical (PEC) cells. This perspective talk will examine how solid-state chemistry principles have contributed both to the design and synthesis of photoelectrode materials for PEC applications related to water splitting, CO2 reduction, and environmental remediation. The design of new-generation oxide semiconductors with the correct optoelectronic and bulk/interfacial chemistry characteristics needed to efficiently drive the above reactions will be addressed. The list of material pre-requisites for efficient solar fuels generation or photocatalytic degradation is daunting and it is hardly surprising that a “magic bullet” material has not emerged even after 4 decades of R&D effort. However, these same challenges have attracted researchers drawn from diverse communities including solid-state/device physics, photophysics/photochemistry, colloid chemistry, ultra-fast spectroscopy, classical inorganic chemistry, environmental chemistry and organometallics. To keep the discussion coherent, only a very limited subset of topics will be addressed in this talk. The progression from binary to ternary, and even quaternary oxides will be examined from the perspective of “band-gap engineering” (a much-maligned word!) and tuning of the interfacial semiconductor surface/fluid energetics. Examples will be drawn from recent research in the speaker’s laboratory and with collaborators.1-4 Acknowledgements The author thanks his collaborators, particularly, Prof. Csaba Janaky (University of Szeged, Hungary) and the National Science Foundation (CHE- 1303803) for partial funding support.

Study of influence of the Ag addition for texturing process of Bi2212/Ag monofilament tapes by image analysis and X ray diffraction

The high Tc superconducting (HTS) materials are now applied in electric power systems. Cables, trans-formers and motors with superconducting tapes are now in test worldwide. However, HTS materials have intrinsic anisotropy that affects the values of their critical currents. Textured HTS samples present improved superconducting properties. The present work describes a study of the texturing process in monofilamentary tapes, using as HTS material the BSCCO system, i.e., 1G HTS tapes (Bi2212/Ag). The purpose of this work is presentation the alternative method for feature in the characterization of texturing in the superconductor ceramics Bi2212 tapes.

Modulation of transport properties of optimally doped La1.85 Sr0.15 CuO4 thin films via electric field modification of the grain boundaries

Modulation of the transport properties of a superconducting La1.85Sr0.15CuO4-based ionic-liquid gated transistor has been achieved. For an applied gate bias Vg ≥ 2 V, the characteristic sheet resistivity vs. temperature (Rs–T) curves exhibit a fully reversible foot feature below the superconducting transition temperature (Tc). In contrast to the behaviour expected from the large charge carrier density of this high-Tc superconductor material, the normal state conductance above Tc also exhibits a large modulation, indicating a larger charge screening length than that predicted from a simple Thomas–Fermi model. We regard these changes as due to electrostatic modification of the charge density at structural imperfections such as grain boundaries present within the sample. Such modification alters the coupling between superconducting domains and dictates the overall Rs–T trend of the gated film. To explain our findings, we employ Mannhart's model of electronic band bending at the grain boundaries and propose that this band bending can be modulated by large electric fields resulting in the observed modulation of the transport properties of the device.

An Overview on the Research of Iron-Based High-T c Superconductors Probed by X-ray Absorption Spectroscopy

The discovery in 2008 of a new family of high-T (c) superconductor (HTSC), i.e., layered compounds based on iron, has spurred a tremendous interest in the community of condensed matter physics. This discovery has broken cuprate "monopoly" in the physics of HTSC materials. Until now, thousands of experimental and theoretical methods were devoted to investigate the superconducting properties of this new iron-based HTSCs. Synchrotron radiation-based X-ray absorption spectroscopy (XAS) made great contributions to the local lattice structure, the electronic structure, and even the superconductive mechanism of this iron-based materials. The aim of this review is a short introduction into the progress of research on new iron-based HTSCs probed by the unique technique-XAS, including the electron correlations, local lattice distortions, changes of valence upon doping or pressure, and even the isotope effect for this new iron-based family.

On the possible key experiments to show the singlet-to-triplet conversion of the Cooper pairs by the use of a SFCO-method

The problem of electron pairing above Meissner expel arose when high-Tc superconductive (HTS) materials were discovered. And scientists are admitting know that there is need to consider 2 processes for HTS: electron pairing and long-range phase coherence among Cooper pairs (pair condensation) – separately and independently each other. Otherwise, it is admitted, that in HTS electrons become paired above Meissner expel (above T0, starting from Tc) & start forming SC-condensate only at T0, while in low-Tc SC materials (LTS) the pairing and pair condensation start simultaneously (T0 = Tc). But, since discovery of HTS new data appeared and importance of some earlier data was recognized, indicating analogy among the HTS and LTS in connection with these 2 processes. Here we show that there are no differences among these materials regarding the said processes: electron pairing and pair condensation are separate & independent even in LTS. Difference is in a temperature scale. For LTS these processes run in a narrow range (∼30mK), while in HTS the scale is longer (for YBaCuO, more than 3K). This is the reason why separation of Tc from T0 in LTS is so hard so far. The problem is still open also due to lack of methods for "nonperturbative" study of the beginnings of SC transition in clean (tiny) objects with small signal. Analysis of data permits to conclude that becomes urgent sensitive study of the Fulde-Ferrell-Larkin-Ovchinnikov superconductivity in heavy-fermion materials that have layered electronic structure. And, the SFCO method may stand key tool for sensitive study of the pair formation in FFLO state. Such a study may show singlet-to-triplet conversion of Cooper pairs. It may also allow separating the ideal conducting (R = 0) & ideal diamagnetic (B = 0) states, which are important for true interpretation of a real nature of superconductivity.

Surface planarization and masked ion-beam structuring of YBa 2Cu 3O 7 thin films

Surface planarization and masked ion-beam structuring (MIBS) of high-T c superconducting (HTS) YBa 2Cu 3O 7-δ (YBCO) thin films grown by pulsed-laser deposition (PLD) method is reported. Chemical–mechanical polishing, plasma etching, and oxygen annealing of YBCO films strongly reduce the particulate density (~ 10 –2 ×) and surface roughness (~ 10 –1 ×) of as-grown PLD layers. The resistivity, critical temperature T c ≈ 90 K and critical current density J c (77 K) > 1 MA/cm 2 of films are not deteriorated by the planarization procedure. The YBCO films are modified and patterned by irradiation with He + ions of 75 keV energy. Superconducting tracks patterned by MIBS without removal of HTS material and, for comparison, by wet-chemical etching show same T c and J c( T) values. Different micro- and nano-patterns are produced in parallel on planarized films. The size of irradiated pattern depends on the mask employed for beam shaping and features smaller than 70 nm are achieved.

EXPLORATION AND SEARCH ON NEW HIGH TC SUPERCONDUCTIVE MATERIALS

On the basis of Fan and Malozovsky theory, which had discussed the non-phonon mechanism of the layered Fermi liquid superconductivity, and of the experimental studies and theoretical analyses obtained by Zhang et al. as well as other scientists, we have analyzed and discussed the extrinsic and intrinsic factors of affecting the transition temperature Tc of cuprate superconductors. We also will present some possible approaches to explore new high Tc superconductive materials, and pay more attention to the non-traditional phonon mechanism, low dimensional or quasi two-dimensional system, and hexagonal structure materials, etc.

Microscopic structural evolution in terms of porosity in high-Tc superconductors

The low critical current densities of high-Tc superconductors materials can be related to the microstructural imperfections such as pores and microcracks, which reduce the effective current carrying cross section.

Vortex States in Strongly Anisotropic HTSC in Parallel Magnetic Field

High Tc superconductors (HTSCs) for the application of magnets and cables are usually used in a magnetic field parallel to the superconducting layers, using the intrinsic pinning of vortices in the layered structures. However, vortex states in the parallel field have not been well understood in strongly anisotropic superconductors. We have studied the vortex states by measuring the flow resistivity of Josephson vortices (JVs). From the measurements, we can determine the 3D-ordered phase of JVs, which means that JVs are well ordered and are considered not to influence the dissipation of the superconducting state. However, by the R-T measurements, we have found the excitation of pancake vortex/anti-vortex pairs to reduce the flow resistance. This limits the application of HTSC materials in the parallel magnetic fields.

Unusual metal-like state in HTSC and CMR oxides

Present report deals with the effect of disorder on Bi-2212 type high Tc superconducting and LCMO type CMR oxide materials. Ion irradiation (50MeV Li3+ beam) creates high level of disorder in the superconducting system and as a result increase of room temperature resistivity (ρ300) has been observed. Radiation induced point defects cause an increased dρ/dT in the metal-like regime of Bi-2212. Similar increase of dρ/dT in the FM (ferromagnetic and metal-like) state has also been found in LCMO system. Enhancement of metal-like behavior is unusual in the sense that a simultaneous decrease of Tmi (metal–insulator transition temperature for LCMO) or Tc (superconducting transition temperature for Bi-2212) due to irradiation has also been observed. Effect of the defects incorporated by other means like variation of heat treatment and ion irradiation has been investigated for a better understanding on the electrical transport in these complex materials. Results have been discussed in the light of their intrinsic granular nature.

Field penetration and field electron emission from HTSC materials

AbstractThis paper discusses field penetration into high‐Tc cuprates under field electron emission conditions. A quasi‐classical approximation based on Thomas–Fermi non‐linear screening theory has been used to discuss field penetration into a high‐Tc superconductor (HTSC) emitter, taking into account the HTSC electronic structure. The numerical results obtained are substantially different from the predictions of linear theory. The results show that, for a screening length of several angströms and field strengths typical of field electron emission spectroscopy, the amount of band‐bending can be comparable with the total width of the band. Thus, the effects of field penetration and band‐bending should be taken into account when constructing a theory of field emission from these compounds. Copyright © 2004 John Wiley & Sons, Ltd.

High-Tc superconducting microbolometer for terahertz applications

Superconducting hot electron bolometer mixers are now a competitive alternative to Schottky diode mixers in the terahertz frequency range because of their ultra wideband (from millimeter waves to visible light), high conversion gain, and low intrinsic noise level. High Tc superconductor materials can be used to make hot electron bolometers and present some advantage in term of operating temperature and cooling. In this paper, we present first a model for the study of superconducting hot electron bolometers responsivity in direct detection mode, in order to establish a firm basis for the design of future THz mixers. Secondly, an original process to realize YBaCuO hot electron bolometer mixers will be described. Submicron YBaCuO superconducting structures are expitaxially sputter deposited on MgO substrates and patterned by using electron beam lithography in combination with optical lithography. Metal masks achieved by electron beam lithography are insuring a good bridge definition and protection during ion etching. Finally, detection experiments are being performed with a laser at 850 nm wavelength, in homodyne mode in order to prove the feasibility and potential performances of these devices.

Electromagnetic behaviour of high- Tc superconducting tapes: a numerical simulation approach

A two-dimensional numerical model that simulates the electromagnetic behaviour of silver-sheathed high- T c superconducting (HTS) tapes carrying AC currents is presented. The model configures the HTS tape as a non-linear conductor whose effective conductivity is a function of the electric field and current density as described by a power-law E– J characteristic. The model has been used to investigate a number of cases for a HTS tape carrying current of various values. Field profiles in the interior of the tape are presented and analysed with reference to the critical state model and the flux creep/flow in HTS materials.

Extraction–Photometric Determination of Thallium in High-TcSuperconducting Materials Using Toluylene Blue

A procedure has been developed for the extraction–photometric determination of thallium as an ion-pair complex with bromide ions and toluylene blue. The procedure allows thallium to be determined in Tl–Cu-containing high-T csuperconducting materials based on Cu, Ca, Ba, Sr, La, Pb, In, and Hg immediately after sample dissolution without separating Tl from its concomitants.

１００ｍ超電導ケーブル実用性検証試験の概要

Since the discovery of High-Tc superconducting (HTSC) materials, elementary technologies of an HTSC cable system have been developed such as the manufacturing technology of a conductor wound with HTSC wires, cold dielectric properties, and thermally insulated pipes. HTSC cable models have also been constructed to evaluate these technologies. As a next step, new test project of a 100m, 66kV/1, 000A/100MVA class, three-core HTSC cable system, integrating these elementary technologies, are planned to verify the practicability of an HTSC cable system as an actual power system equipment. It is a joint project of Tokyo Electric Power Company and Sumitomo Electric Industries, Ltd., and is being conducted in collaboration with the Central Research Institute of Electric Power Industry. The purposes of this project are to prove newly developed technologies satisfying the requirement as actual deployments, to prove manufacturing abilities and installation technologies, and to conduct long-term current-voltage loading tests. The cable consists of three-core conductors placed in thermally insulated pipes having a vacuum insulation layer between them. Each conductor consists of a copper former, superconducting layers, PPLP/LN2 composite insulating layer, and superconducting shielding layers. The cable is placed at a CRIEPI test yard and is bent into U-shape at its center, partially installed into a duct 150mm in inner diameter. The following tests are scheduled, using this cable system, such as an initial cooling test, continuous rated current-voltage loading tests, load fluctuation tests, cooling cycle test between room temperature and LN2 temperature, and overloading and overvoltage withstand tests. Through these tests, problems are expected to be extracted that may be difficult to foresee in individual part tests for development of an actual level HTSC power cable system.

A high-Tc superconductor material model for timeharmonic numerical computations

An alternative material model for sinusoidally excitedsuperconductors or other nonlinear conductors is proposed. It is based on anonlinear power-law relation between a current density and an electric field. Sincethe answer to a harmonic excitation is therefore nonharmonic, usually a fullytime-dependent analysis is required. Using the finite-element method in twodimensions, a nonlinear but harmonic analysis is defined. This is achieved byconstructing an effective conductivity which models the average materialproperties during one period of the excitation. The nonlinear equation systemis solved with the complex Newton-Raphson method. The obtained results agreewell with more exact time step solutions. The new method is much more timeeffective and is not restricted to two dimensions.