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

Temperature dependence of resistivity of porous silicon formed on N-substrates

Results of measurement of resistivity of mesoporous silicon formed on n-type substrates in a wide temperature range are presented. Measurements show that at low temperatures there is a growth of resistance of four orders of magnitude compared to that at room temperature which occurs in a relatively narrow temperature range. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2063

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