Dynamics Of Josephson-junction Arrays Research Articles

Possible dynamics of Josephson junction arrays connected to high-Q tank circuit

Serial Josephson junction arrays connected to high-Q tank circuit are analysed and discussed. Numerical simulation of the systems shows two possible oscillation modes above resonance frequency when the tank impedance is capacitive. These are the inphase oscillation mode and the collectively antiphase oscillation mode. This fact is responsible for complicate switching dynamics, which can block parametric resonance excitation. Stability domains of the modes depend on McCumber parameter of the junctions. Increase in this parameter is favourable to the inphase mode. When the inphased oscillations are feasible, the resonance peak-like peculiarities on IV curve and Shapiro steps can be described with the analytic theory derived earlier for one-junction case and extended over the array systems.

Superconductor-Insulator Transition in a Tunable Dissipative Environment

We study the influence of a tunable dissipative environment on the dynamics of Josephson junction arrays near the superconductor-insulator transition. The experimental realization of the environment is a two dimensional electron gas coupled capacitively to the array. This setup allows for the well-controlled tuning of the dissipation by changing the resistance of the two dimensional electron gas. The capacitive coupling cuts off the dissipation at low frequencies. We determine the phase diagram and calculate the temperature and dissipation dependence of the array conductivity. We find good agreement with recent experimental results.

Vortex dynamics in disordered Josephson junction arrays: From plastic flow to flux flow

We study the dynamics of Josephson junction arrays with positional disorder and driven by an external current. We consider weak magnetic fields, corresponding to a frustration f = n + 1 25 with n integer. We find that above the critical current i c there is a plastic flow of vortices, where most of the vortices are pinned and only a few vortices flow through channels. This dynamical regime is characterized by strong fluctuations of the total vorticity. The number of the flow channels grow with increasing bias current. At larger currents there is a dynamical regime characterized by the homogeneous motion of all the vortices, i.e. a flux flow regime. We find a dynamical phase transition between the plastic flow and the flux flow regimes when analyzing voltage-voltage correlation functions.

Numerical study of self-field effects on dynamics of Josephson-junction arrays

We consider the influence of self-induced magnetic fields on dynamic properties of arrays of resistively and capacitively shunted Josephson junctions. Self-field effects are modeled by including mutual inductance interactions between every cell in the array. We find that it is important to include all mutual inductance interactions in order to understand the dynamic properties of the array, in particular subharmonic structure arising under AC current bias.

Effect of current direction on the dynamics of Josephson-junction arrays.

We present an extensive experimental and theoretical study of the effect that the current direction has on the dynamical properties of rf and dc current-biased overdamped Josephson-junction arrays. We show that a strong {ital spatial} {ital symmetry} of the array about the direction of the macroscopic current flow is necessary for arrays to show {ital only} nteger giant Shapiro steps. If this symmetry is broken, arrays will produce {ital both} fractional {ital and} integer giant Shapiro steps. A moving-vortex model and a pendulum model are used to describe our experimental and computational results.