Well-defined zigzag-shaped ramp-type Josephson junctions between YBa 2 Cu 3 O 7 and Nb have been studied. The magnetic field dependencies of the critical currents provide evidence for d-wave-induced alternations in the direction of the Josephson current between neighboring sides of the zigzag structure. The arrays present controllable model systems to study the influences of p facets in high-angle high-T c grain boundaries. From the characteristics, we estimate a possible imaginary s-wave admixture to the order parameter of the YBa 2 Cu 3 O 7 to be below 1%.
High-T c SNS-type Josephson junctions and DC SQUIDs were successfully fabricated using hetero-epitaxially grown multilayers of YBa2Cu3Ox and PrBa2Cu3Ox. These layers are c-axis oriented and hence edges of the muir[layers give rise to a current flow in the ab-plane between the electrodes of a Josephson junction. The necessary structuring was done by Ar ion beam etching. The individual junctions exhibit a supercurrent up to 80 K. The IcR,-product of these junctions usually has a lower limit of 8 mV at 4.2 K. Voltage modulation of the first DC SQUIDs can be observed up to 66 K. Details on the fabrication and measurements are presented.
A surface plasmon based chemooptical sensor has been optimized by the use of computer simulation programs. Calculated and experimentally measured performances are in good agreement, showing the value of the simulation tool.
We analyzed the transport of charge carriers across PrBa2Cu3−xGaxO7−δ (PBCGO) barriers as a function of barrier thickness, Ga-doping level, temperature, and bias voltage. It was found that by Ga doping, the normal state resistance (Rn) of the junctions was systematically increased, while the critical current (Ic) remained constant. We argue that pair transport takes place by direct tunneling, whereas the quasiparticles have access to channels formed by one or more localized states inside the barrier. By Ga doping the IcRn products were increased, up to 8 mV at 4.2 K for junctions with 8 nm thick PrBa2Cu2.6Ga0.4O7−δ barriers.
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