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By use of a recently developed multi-scale simulation method, we re-investigate terahertz wave emission with motions of Josephson vortices, as a possible mechanism for enhancing the emitted power. Results show that there appears a strong wave emission around the n = 2 cavity mode (one-wavelength mode), when motions of vortices and cavity modes are resonate.

We look for chaos in an intrinsically coupled system of Josephson junctions. This study has direct applications for the high-Tc resonators which require coherence amongst the junctions.

We report on a process for fabricating YBCO interface-engineered junctions on sapphire substrates. The electrical properties of the junctions thus produced were investigated across a wide range of temperatures. The current-voltage characteristics approached the characteristic of the resistively shunted junction property at high temperatures. The I C R N products of the junctions displayed a quasi-linear property. The I – V characteristics showed Shapiro steps under irradiation at 12.3 GHz, and this is consistent with the Josephson relation. We predict that the interface-engineered Josephson junction on sapphire will be suitable for ractical use in high-frequency mixers after optimization of the fabrication process.

Current–voltage ( I – V ) characteristics have been investigated experimentally for a square Josephson array with a dilute vortex density f . Critical scaling analyses of the I – V data indicate that vortices in the real array undergo a melting transition directly from the pinned-solid phase to the liquid phase at T c ∼0.3 J / k B for 1/50⩽ f ⩽1/8. Such high melting-transition temperatures and the absence of depinning transition from a pinned-solid phase to an intermediate floating-solid phase are in disagreement with previous theoretical predictions.

We numerically study the dc Josephson current in d-wave superconductor/normal metal/d-wave superconductor junctions by using the recursive Green function method. The Josephson current is sensitive to the orientation angle between the crystalline axis of the high- T c superconductors and the normal of the junction interface. It was pointed out that the ensemble average of the Josephson current, 〈 J 〉, vanishes when the orientation angle is π /4 and the normal metal is in the diffusive transport regime. We show in this paper that 〈 J 〉 disappears even when the normal metal is in the quasi-ballistic transport regime.

We have investigated current-voltage (I-V) characteristics of intrinsic Josephson junctions in c-axis-oriented (Bi,Pb)2Sr2Ca2Cu3O10+x (Bi-2223) superconductive thin films. Clear branching structures peculiar to stacked junctions are observed. We also have evaluated the quasi-particle current of a single intrinsic junction by adopting the modified mesa structure. The obtained quasi-particle I-V curve is quite well explained theoretically by assuming dx2−y2 symmetry for the superconductivity order parameter.

We observed the Josephson effect with hysteretic I − V characteristics on lateral-type grain boundary junctions using Y 1 Ba 2 Cu 3 O 7 − δ (YBCO) and Bi 2 Sr 2 Ca 1 Cu 2 O 8 + δ (BSCCO) films. In the case of YBCO, grain boundaries consisting of an a -axis oriented needle-like grain surrounded by c -axis oriented grains are used for Josephson junctions. The junctions using as-grown films without annealing did not show hysteretic I − V characteristics, but they show RSJ-type I–V characteristics with no hysteresis. After appropriate annealing in pure Ar, this junction property changes to have hysteretic I − V characteristics. In the case of BSCCO, grain boundaries consisting of a (110) oriented needle-like grain surrounded by (001) oriented grains are used. Hysteretic I − V characteristics are observed for the sample, indicating the presence of the intrinsic Josephson effect caused by stacked CuO 2 double layers along the c -direction.

We have measured I c R n of intrinsic Josephson junctions in Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212). Self-heating was minimized by applying pulse currents of less than 1 μs duration time and the current-voltage ( I - V ) characteristics up to the normal region were measured. The value of I c R n obtained was around 22 mV, which was larger than the values that have ever been reported of high- T c Josephson junctions.

In inhomogeneous Josephson junctions the Eck peak characterizing the current-voltage characteristics is predicted to be replaced by a rather different yet prominent feature whose location and shape strongly depend on the strength of the applied magnetic field and the spatial correlations of the associated distorted Abrikosov flux lattice.

We report on the c -axis current-voltage ( I - V ) characteristics in Bi 2 Sr 2 CaCu 2 O 8+x single crystals. The I - V characteristics exhibited multiple branches, and the critical current modulated under the magnetic field perpendicular to the c -axis. These results confirm the idea that the crystal behaves as an array of Josephson junctions.

Modulated microwave absorption shows that as-grown crystals of Nd 2− x Ce x CuO 4 already contain superconducting regions prior to reduction, which then increases the measured T c from 7 to 21 K. The temperature dependence of the modulated absorption has a maximum near T c , indicating the reduced role of weak Josephson junctions in these crystals compared to ceramic samples of the cuprate superconductors.

We use the Deutscher-Muller model of depressed order-parameter Josephson junction coupling [1] to describe the HTSC ceramics, modeling them as simple granular superconductors. The low critical current density of the ceramics ( J c ≈10 3 A/cm 2 ) can thus be understood within the framework of a simple model of grains, which are coupled by Josephson junctions with depressed order-parameters. An explicit solution for the gap equations is given, and typical numerical values are computed for YBCO, showing good agreement with experimental data.

Quantum dynamics of the phase difference in small square-shape d x 2 - y 2 -superconductors (d-dot) embedded in a s-wave superconducting matrix is investigated. The effective Hamiltonian for the system containing two d-dot’s that are located closely and coupled inductively is derived.

The two superconducting transitions (Tc1 and Tc2) were observed in a single crystal Br2Sr2Ca1–xGdxCu2O8−σ transition at Tc1 is attributed to the superconductivity occurring in the CuO2 “cell” intra-layers, while the pseudo transition at lower temperature Tc2 is clealy induced by the Josephson coupling in “blocking” layers between the CuO2 “cell” layers.

The expression for critical current dependence on magnetic field for self-similar chain of parallely-connected Josephson junctions has been calculated. The fractal dimension has been obtained.

The present study provides an improved ESR spectrometer and a useful method which make it possible to separate two kinds of magnetizations trapped in the bulk and at Josephson junctions of superconductors, based on the characteristics of two component microwave responses previouly found.

The coherence lenghts of some layered superconductors are comparable to or smaller that the interlayer distance, i.e. the layered crystal structure is mapped to a periodic order parameter modulation. In our measurements on (Bi 1−x Pb x ) 2 Sr 2 CaCu 2 O 8+ϑ , IBi 2 Sr 2 CaCu 2 O 8 , Tl 2 Ba 2 Ca 2 Cu 3 O 10 , Pr 2−x Ce x CuO 4 +ϑ and κ-(BEDT-TTF) 2 Cu(NCS) 2 single crystals with transport perpendicular to the layers, we were able to detect the DC as well as the AC Josephson effects.

Propagating plasma modes have been observed for the first time in a very thin superconducting film of granular aluminium deposited on a high dielectric constant material in the 100 MHz-1 GHz frequency range. The two-dimensional plasma dispersion relation, taking account of retardation effects, has been verified.

We describe a “bi-epitaxial” process to create 45 degree grain boundary Josephson junctions in YBa 2 Cu 3 O 7 . These bi-epitaxial grain boundary Josephson junctions are defined by standard photolithographic technique, and appear to be readily extended to integrated circuits. Some transport properties are reported and compared to other types of grain boundary Josephson junctions.

We report on measurements of DC and AC Josephson effects in small sized Bi 2 CaSr 2 Cu 2 O 8 single crystals. The results are consistent with the assumption that adjacent CuO double layers are coupled via Josephson mechanisms.

We have studied the stationary Josephson effect on YBa 2 Cu 3 O 7− δ ( T c =90 K ) and Bi 2 Sr 2 Ca 1 Cu 2 O 8 ( T c =80 K and 87 K for two samples of different origin ) ceramic based junctions. The temperature dependence of the critical current near T c has been found as I c ≈( T c - T ) 3 2 for the Y-Ba-Cu-O samples indicating that they should be classified as S-N-I-N-S type junctions. The I-V curves of the Bi-Sr-Ca-Cu samples show the typical behaviour of S-I-S structures. Using Ambegaokar-Baratoff's theory for Bi 2 Sr 2 Ca 1 Cu 2 O 8 , the temperature dependence of the superconducting state gap Δ( T ) was calculated and it was evaluated that 1.45⩽2Δ(0)/ k B T c ⩽3.5.

The behaviors of superconductive glass state in single phase GdBa 2 Cu 3 O 7−y , YBa 2 Cu 3 O 7−y ceramics have been studied systematically by measuring the microstructure, superconductive parameters, I–V characteristics, etc.. The grain-boundary Josephson effect and percolation nature etc. have been observed and explained satisfactorily with 3-D network of Josephson junctions.

Measurements of the complex ac conductance of sputtered YBaCuo films reveal, in the critical transition region, features strikingly similar to those observed at the phase transition of artificially prepared two-dimensional Josephson junction arrays.

A quantum Monte Carlo study of a two-dimensional array of Josephson junctions including the effects of Josephson tunnelling and long-range Coulomb interactions has been performed. The inclusion of long-range interactions does not measurable shift the location of the Berezinskii-Kosterlitz-Thouless transition.

Crosspiece with dimensions of (10 -2 cm) 3 containing the stable superconducting weak link has been made of ceramic with T c ≅ 90K. Its properties similar to that of the single Josephson junction has been obtained during experiments in the rf-SQUID (1) steps with n = 0 / 100 (35.5 GHz at 77 K) are being studied.