J. Scherbel

One-dimensional intrinsic Josephson arrays based on HTS thin films

Abstract Mesa structures were produced from different highly anisotropic HTS thin films showing the intrinsic Josephson effect in c -direction. We observed clear dependencies of the critical current on both external magnetic field and microwave field. For the first time we were able to detect the modulation of the critical current of BSCCO thin film mesas in external magnetic field. For BSCCO as well as for TBCCO we found modulation periods in the Tesla range which is in good agreement with the lateral dimensions of the junctions. In the current-voltage characteristics of TBCCO mesas we found subgap structures and measured their dependence on temperature, external magnetic field and microwave irradiation.

Synchronization of serial intrinsic Josephson junction arrays on vicinal substrates

A resonator together with a resistive shunting cover over the microbridge was applied to synchronize intrinsic Josephson junctions. We made both numerical and experimental investigations of the electrical properties of such microbridges: the multibranch behaviour above critical currents and switching between branches. The stability analyses revealed that in-phase states are sensitive to noise. Optimal parameters for synchronization of the system of two junctions up to 26–27% spread of critical currents are calculated.

Phase locking in a stack of two Josephson junctions with a sidewall shunt

Abstract The coherent behaviour (phase locking) was investigated by the method of slowly varying amplitudes for different inductances of the shunt as well as for different capacitances of junctions. The existence of thresholds of phase locking at small inductances as well as at large inductances was explained in the developed model.

Thin film series arrays of intrinsic Josephson junctions

The intrinsic Josephson effect between the CuO2 sheets in Tl-2212 and Bi-2212 was used to prepare thin film mesa structures acting as series arrays of a number of junctions corresponding to the height of the mesa. We investigated the electrical properties of these arrays at various temperatures, in external magnetic fields, and under irradiation of microwaves. The results are discussed within simple theoretical models of 1-D Josephson arrays.

The Resonant Interaction of Intrinsic Josephson Junctions With Standing Waves

IV-characteristics of shunted microbridges made of Tl2Ba2CaCu2O8 (TBCCO) were measured. The TBCCO films were grown epitaxially on 20° misaligned LaAlO3 substrates and then covered by the gold shunting layer. Each of the microbridges consisted of about 360 shunted intrinsic Josephson junctions. Self-induced resonant particularities with a main period of about 17 mV were found on IV-curves. We showed that these particularities did not depend on the characteristics of the individual junctions and that they were connected with the geometrical dimensions of the system. The origin of particularities was the interaction of Josephson generation with the standing wave appeared in the system. We modeled this interaction considering radiation of junctions into the transmission line and found that the model described the main resonant structure of IV-characteristics. Strong synchronization of junctions appeared in the vicinity of the first particularity.

Coherent radiation in serial arrays of Josephson junctions

We measured IV-characteristics of a planar array of about 362 shunted intrinsic Josephson junctions in microbridges made from the Tl2Ba2CaCu2O8 layers which were grown epitaxially on 20° misaligned LaAlO3 substrates. The IV-characteristics contained resonant particularities (jumps of voltages) with a main period of 17 mV. We showed that the origin of particularities was the interaction of Josephson generation with the internal resonant mode of the system. We modeled this interaction considering the radiation of junctions into the transmission line and found that strong synchronization of junctions appeared in the vicinity of the first particularity. The estimate of the ac power emitted into free space was 0.05-0.1 microwatt, whereas the power of 0.3-0.5 mW was emitted inside the resonant system.