Papers by Keyword: Josephson Junction

Abstract: In this article we consider the modulation of the plasma frequency switching current-phase dependence of Josephson systems based on the CuO2 harmonic mode into the anharmonic one. It is established the increase of the plasma frequency in the cuprate high-temperature superconductors arising due to deviation of dependence current-phase between the oxide planes in high-temperature superconductors from the standard sine wave form.

Abstract: This paper investigates the generalized synchronization of chaotic dynamics in resistive capacitive inductance (RCL)-shunted Josephson junctions with uncertain parameters.Based on Lyapunove stability theory and adaptive control method, unified nonlinear feedback controller and the parameter update laws are pesented .Numerical simulation illustrate that the system can realize generalized synchronization by different scaling factors .

Abstract: For chaotic behavior appearances in Josephson junction of resistance-capacitor-inductor driven by the direct-current and in order to eliminate lateral oscillations of Josephson junction and dispel their adverse effect on the system performance or the working conditions of the system, the chaotic system of Josephson junction was analised. First, the complex dynamic characteristics of chaos were gave, including the phase trajectory map, Lyapunov index, bifurcation diagram. It proved the objective existence of chaos and the parameter range of the chaotic occurrence in Josephson junction system through the analysis of these characteristics. In order to eliminate chaos of the system, a new controller was designed, which contains only one controller term.. And it can control the system stability at the equilibrium point O(0,0,0). The results show that this method is effective, and constructing controller is simple, and the system after controlled has shorter dynamic response time and good robustness.

Abstract: In this work we present the technology of preparing multilayer MgB₂ superconducting films via CVD method. The first layer of the MgB₂ superconducting film was obtained by two-step method: growthing the precursor boron film on a polycrystalline Al₂O₃ substrate first, then post annealing the film in magnesium ambient, thus we got the first layer of MgB₂ film. After that a pure boron film was deposited on the MgB₂ film , acting as the medium insulating layer, finally the second layer of the MgB₂ superconducting film was formed by in-situ growth, evaporated magnesium atoms and boron atoms that decomposed from diborane met near the substrate and generated the second layer of the MgB₂ superconducting film. The square resistance of the boron medium insulation layer is higher than 20 MΩ. The transition temperature of the both superconducting films was above 38 K, and the temperature for zero resistance is above 37 K. We found that different thickness of the B layer made different I-V curve between two superconducting films, which is very important for the use of Josephson junction. More meaningful results can be expected as the experiment goes on.

Abstract: Thin films of iron pnictides open the way for fundamental experiments on superconductivity in this material. Thus we started to develop tunneling and Josephson junctions with pnictide film electrodes. Different preparation methods for Josephson junctions were investigated and the first results are presented. Resistive measurements show a high superconductive transition temperature of about 20 K even for the La-1111 electrode after patterning and preparation of the tunneling window. The hybrid junctions were completed with a PbIn counter electrode and normal conducting gold layers as barriers.

Abstract: We describe recent topics of rapid-single-flux-quantum (RSFQ) circuits. Much higher integration and higher-speed operation are required for commercializing the RSFQ circuits in any application. To satisfy this requirement, we measure several kinds of time fluctuations that possibly limit the integration level and operating speed, and introduce the flexible passive transmission line technology including a multicasting transmitter. In addition, we describe our ongoing applications. A multiple-detectors-system is expected to open a new application field of an RSFQ-based analog-to-digital converter and a digital signal processor. As for a microprocessor application, increased number of arithmetic logic units may be effective for enhancing the computing performances.