Dynamische Eigenschaften und Wechselwirkungen von Hochtemperatur Josephson-Kontakten
Kunkel, G. (Corresponding author)
Publikationen vor 2000; PRE-2000; Retrocat
Jülich Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag 1996
II, 121 p.
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Berichte des Forschungszentrums Jülich 3192
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Please use the identifier: http://hdl.handle.net/2128/21601 in citations.


The dynamic properties and mutual interactions ofhigh-temperature Josephson junctions have been investigated. The direct observation of Josephson oscillations is one of the best methods to investigate the dynamics ofJosephson junctions. The Josephson radiation from different types of YBa$_{2}$Cu$_{3}$O$_{7}$ (YBCO) thin film junctions, including step-edge, SNS with N = Au or N= PrBa$_{2}$Cu$_{3}$O$_{7}$, bieptaxial and bicrystal junctions, has been analyzed, therefore. The radiation was detected using a nonresonant radiometer system with a receiving frequency of 11 GHz. Most junctions exhibited a large emission peak at a voltage which was related to the detection frequency by the second Josephson relation. Typically, for high temperatures, and, therefore, small critical currents, the measured radiation linewidth agreed weIl with theoretical predictions. In this temperature range, the Josephson junction could be considered as an electrically short junction (w/$\lambda_{j} \le$ 4). At Iower temperatures, the experimentallinewidths typically deviated from the theoretical values based on the RSJ - model It is suggested that in the so called Iong junction limit (w/$\lambda_{j}$ > 4), flux motion is responsible for additionalnoise. The mutual interactions were, in a first step, studied by the phase Iocking oftwo YBCO stepedge Josephson junctions. The junctions were coupled by a feedback Ioop consisting of an inductor and a resistor. The results showed phase synchronization up to 500 GHz, only limited by the time constant of the feedback Ioop. This interaction was observed up to 50 K Simulations based on the rsj - model, with parameter values extracted from the experimental data, confirmed the dc measurements. Strong Fiske resonances in medium damped Josephson junctions enhanced the Iocking strength by an order of magnitude. In a second step, microwave circuits using small 1-dimensional junction arrays have been developed. In these circuits, up to ten parallel-biased YBCO Josephson junctions were utilized to demonstrate phase-Iocking for applications such as oscillators. The basic ceIl consisted oftwo Josephson junctions enclosed in a microstrip resonator which provides voltage-locking and low dynamic resistance in the current-voltage characteristic. Synchronization of al ten junctions was observed up to 45 K and up to 1 THz. The power generated by a five junction array was measured with a detector junction on-chip. The Josephson oscillations of a ten junction array were direcdy detected with a radiometer between 70 and 124 GHz. Power and linewidth showed clear evidence for the mutual interactions in these parallel-biased circuits. In conclusion, phase locking of up to ten high-temperature Josephson junctions has been demonstrated. Strong resonances, induced by a coplanar microstrip resonator, produced very strong coupling between the junctions and low radiation linewidths. These arrays are promising candidates for on-chip applications in the mm- and sub-mm-wave region.