Multiple Quantum Flux Penetration in Superconducting Loops

The dynamics of flux entry into a superconducting loop interrupted by a thin-film Josephson junction have been studied experimentally. A computer simulation of the system yields excellent agreement with these data. It is found that a specific number of flux quanta will bubble into a loop, and that this number depends only on the relative damping which is present

Probing the Phase-Dependent Conductance and Nonequilibrium Properties of Josephson Junctions by Means of Flux Entry into Weakly Closed Loops

Numerical simulations have shown that the relative number of flux quanta which penetrate a weakly closed superconducting loop depends upon the magnitude and sign of the phase-dependent conductance. We examine the possible use of this dependence as an experimental probe of the cosy term and nonequilibrium properties of Josephson junctions

Intermittent Synchronization of Resistively Coupled Chaotic Josephson Junctions

Numerical simulations have been used to investigate the dynamics of a pair of resistively linked Josephson junctions with ac bias. For suitable choices of parameters, the chaotic states of the two junctions become intermittently synchronized. Intervals of synchronization are interleaved between bursts of desynchronized activity. The distributions of these laminar times and their dependence on the coupling strength are determined. The role of phase winding in the definition of synchronization intervals is considered

Intermittent Synchronization in a Pair of Coupled Chaotic Pendula

Numerical simulations have been carried out for a pair of unidirectionally coupled identical pendula under the action of a common external ac torque. Both the master pendulum and the slave pendulum were in chaotic states. The only form of persistent locking appeared to be a computational artifact; otherwise the synchronization of slave to master was found to be intermittent

Chaos and Thermal Noise in a Josephson Junction Coupled to a Resonant Tank

Selected dynamical modes are investigated for the autonomous system formed from a dc biased Josephson junction which is resistively coupled to a resonant tank. A hysteretic zone in the current-voltage characteristic is shown to result from coexisting chaotic and periodic states. The detailed features of these states, including the geometrical structure of the attractors and their basins of attraction, as well as thermally induced transitions between them, are explored

Multiple-Quantum-Flux Penetration in a Superconducting Loop Containing a Josephson Junction: Temperature Dependence

A temperature-dependent resistivity shunted junction (RSJ) model with a piecewise linear quasiparticle characteristic has been used in simulations to predict the flux dynamics in a superconducting ring containing a single Josephson junction. The computed results for relative flux penetration do not agree well with experimental data at temperatures approaching Tc . This indicates either that the subgap damping is not directly deducible from junction tunneling characteristics, or that the RSJ model is not sufficiently general in this situation

Chaos in a Parametrically Damped Pendulum

Numerical simulations have shown that a parametrically damped, but otherwise undriven pendulum possesses many of the dynamical modes characteristic of a simple driven pendulum, yet with notable differences. Over most of the parameter space only a stationary steady state is possible. A single domain exists within which are situated three distinct subregions of periodic, multiperiodic, or chaotic motion. The periodic orbits generally occur at half the damping modulation frequency. All of these phenomena have been experimentally observed on an actual pendulum in which parametric damping is generated electronically

Proximity Effects and the Generalized Ginzberg-Landau Equation

A computer program has been developed which finds solutions of the generalized Ginzburg-Landau equation subject to de Gennes\u27s boundary conditions. The resulting information on the spatially varying order parameter is then interpreted vis-a-vis experimental data on both superconductor-insulator-normal-metal —superconductor Josephson tunneling systems, and ultrasonic-surface-wave attenuation

Waveform Display for Slowly Varying Signals

Slowly changing signals will appears on an oscilloscope as a moving dot. A circuit is described which permits such waveforms to be fully displayed in real time. The oscilloscope screen functions as a window across which the signal scrolls at a user selectable rate

Stochastic Noise and Chaotic Transients

Numerical simulations have been used to determine the inhuence of stochastic noise on the lifetimes of chaotic transients. The general literature on the subject of noise and chaos appears to suggest that there should be a significant noise dependency, but remarkably none vvas found for the model systems reported here. These null results are confirmed by direct measurements from an electronic analog of one of the systems