Observation of vortex dynamics in two-dimensional Josephson-junction arrays

Direct observation of vortex dynamics in two-dimensional Josephson-junction arrays

“…A vortex model is used for interpretation of the images. Earlier results for the limit of low vortex density in two-dimensional arrays may be found in [6]. from our investigations important conclusions on the optimization of Josephson junction arrays for oscillator applications can be drawn.…”

Self-field effects in Josephson junction arrays

“…24 When comparing the thresholds obtained numerically with those observed experimentally it is quite arbitrary to decide how small the screening current should be to lead to the disappearance of the signal measured by the LTSEM; therefore a detailed quantitative comparison is not possible on the basis of the results shown here. However, the measured threshold for an array 10ϫ10 critically damped (␣Ӎ1) is ␥Ӎ4, 24 a region where our simulations predict that the screening current is small: I s m Ӎ0.16 or roughly 4% of the bias current at most, i.e., for f ϭ0.5.…”

“…16,17 Finally, there are reasons to believe that there might be a connection between the presence of significant screening currents and the phenomenon of ''row switching'' observed with the technique of LTSEM. 24 It is worth recalling that we have ͑a͒ neglected any spread of the parameters and ͑b͒ retained self-inductances only and neglected mutual inductances. …”

“…24 If the hypothesis that the two thresholds are related is true, it is possible to go further and to speculate that the coherent emission from Josephsonjunctions arrays is related to the presence of non-negligible screening currents.…”

Spatially resolved detection of mutually locked Josephson junctions in arrays

“…Current biasing the array above its critical current, we usually observe beam induced additional voltages ⌬V(x 0 ,y 0 ) from the array. [18][19][20] This voltage difference is recorded as a function of (x 0 ,y 0 ), yielding spatial information. For increasing the sensitivity, the electron beam is chopped at a frequency of about 20 kHz and the voltage response ⌬V is measured with a lock-in amplifier.…”