Long Josephson junctions with spatially inhomogeneous driving

The phase dynamics of a long Josephson junction with spatially inhomogeneously distributed bias current is considered for the case of a dense soliton chain (regime of the Flux Flow oscillator). To derive the analytical solution of the corresponding sine-Gordon equation the Poincare method has been used. In the range of the validity of the theory good coincidence between analytically derived and numerically computed current-voltage characteristics have been demonstrated for the simplest example of unitstep function distribution of bias current (unbiased tail). It is shown, that for the considered example of bias current distribution, there is an optimal length of unbiased tail that maximizes the amplitude of the main harmonic and minimizes the dynamical resistance (thus leading to reduction of a linewidth).Comment: 7 pages, 5 figure

Bridging the terahertz gap for chaotic sources with superconducting junctions

We observe a broadband chaotic signal of terahertz frequency emitted from a superconducting junction. The generated radiation has a wide spectrum reaching 0.7 THz and power sufficient to drive on-chip circuit elements. Our experimental finding is fully confirmed by numerical modeling based on microscopic theory and reveals the unrealized potential of superconducting systems in chaos-based terahertz communication, fast generation of true random numbers, and noninvasive terahertz spectroscopy

Erratum: A one-dimensional tunable magnetic metamaterial (Optics Express)

We have detected an error in our data retrieval script which prepares the measured transmission data for the conversion to magnetic permeability. Correcting this error requires modification of Fig. 4(b) and Fig. 5 in the original publication. All methods, calculations and the conclusion in the published paper are still correct

Experimental and theoretical characterisation of Josephson self-coupling in sub-terahertz flux-flow oscillator

We present experimental and numerical results for a flux flow oscillator based on superconducting Josephson junctions. Our computationally efficient theoretical model takes into account Josephson selfcoupling of the flux flow oscillator and is in a good agreement with our experimental results and previous studies

Radiation linewidth of a long Josephson junction in the flux-flow regime

Theoretical model for the radiation linewidth in a multi-fluxon state of a long Josephson junction is presented. Starting from the perturbed sine-Gordon model with the temperature dependent noise term, we develop a collective coordinate approach which allows to calculate the finite radiation linewidth due to excitation of the internal degrees of freedom in the moving fluxon chain. At low fluxon density, the radiation linewidth is expected to be substantially larger than that of a lumped Josephson oscillator. With increasing the fluxon density, a crossover to a much smaller linewidth corresponding to the lumped oscillator limit is predicted.Comment: 11 pages LaTeX, to appear in Phys Rev

Josephson flux-flow oscillators in nonuniform microwave fields

We present a simple theory for Josephson flux-flow oscillators in the presence of nonuniform microwave fields. In particular we derive an analytical expression for the I−V characteristic of the oscillator from which we show that satellite steps are spaced around the main flux-flow resonance by only even harmonics of the rf frequency. This result is found to be in good agreement with our numerical results and with experiments

Phase locking and flux-flow resonances in Josephson oscillators driven by homogeneous microwave fields

We investigate both analytically and numerically phase locking and flux-flow resonances of long Josephson junctions in the presence of homogeneous microwave fields. We use a power balance analysis and a perturbation expansion around the uniform rotating solution to derive analytical expressions for IV curves. The dependence of the flux-flow step on the amplitude of the rf field and the appearance of satellite steps are explained. As a result we show that satellite steps around the main flux-flow resonance are spaced by both odd and even harmonics of the rf frequency. An analytical expression for the locking range in current of the phase-lock steps is also derived. These results are found to be in good agreement with numerical results

NONEQUILIBRIUM PHENOMENA IN VARIABLE THICKNESS BRIDGES OF SUBMICRON DIMENSIONS

Les particularités du comportement de ponts d'épaisseur variable de dimension submicronique, dues aux électrons hors d'équilibre dans la liaison faible ont été étudiées en présence de courant continu et d'ondes micrométriques.Peculiarities of the behaviour of submicron variable thickness bridges caused by the influence of nonequilibrium electrons in the weak link region have been investigated in the presence of dc and microwaves