The effect of junction resistance on coupling between the microwave and the Josephson tunneling junction

T.V. Rajeevakumar, John X. Przybysz, J. T. Chen

Yuxing Dai, G.J. Cui, Xiangchao Meng +1 more

Adir M Luiz, R. Nicolsky

It has been shown recently that the current-voltage characteristic of a metallic (non-tunneling) Josephson junction could exhibit a negative differential resistance at low voltages, as a predictable and reproducible effect. This letter shows an alternative procedure to generate non-Josephson microwaves (in the cm and mm range) taking advantage of this effect. It is shown that, instead of obtaining harmonic oscillations with the AC Josephson effect, it is possible to generate microwaves using the averaged IVC (current-voltage characteristics) of a SNS junction (a Josephson junction which exhibits no tunneling and has no hysteresis in the IVC).

Kazuhiro Yoshida, K. Hamasaki, Fumi Irie +1 more

Michael R. Scheuermann, J. T. Chen, Jhy-Jiun Chang

The effects of microwave radiation on the vortex modes of Josephson tunnel junctions have been examined. Current steps are induced on the resistive branches at voltages V=(n/m)(hν/2e) where n and m are integers and ν is the frequency of the incident radiation. The system we have studied is a well-defined one in which vortices undergoing periodic motion interact with the periodic perturbation of the microwave radiation. Vertical steps are induced when resonance occurs.

S. Rudner, T. Claeson

Unexpected partly dramatic temperature dependences were registered for the basic tunnel parameters used to characterize a Josephson junction. Measurements of the magnetic field variation of the microwave-power reflection, i.e., a mapping of the Josephson plasma resonance, enabled determinations of the rf small-voltage resistance RJ, the cosφ amplitude ζ, and the effective junction capacitance C in both Pb-O-Pb and PbTl-O-Pb junctions. The uncertainties in the parameter values are large, particularly in the low temperature values of ζ, for which we confirm earlier estimates of ζ, but as the superconducting transition temperature Tc is approached, ζ increases rapidly and goes through a positive maximum close to +1 before it decreases towards zero at Tc. Also, RJ displays a pronounced maximum in the same temperature interval; it decreases rapidly within a narrow range below the temperature of the maximum before it again increases slowly well below Tc. The location in temperature for the two maxima depends upon the barrier via the critical current density, but seems to be material independent. Well below Tc, the ratios of RJ to the normal-state tunnel resistance are also affected by the barrier transmission. These latter properties seem hard to explain within a model based only on the relaxation of the order parameters in the superconductors. A considerable decrease in C close to Tc can be explained by temperature-dependent surface losses in the junction electrodes. The Q-value associated with these could be determined as a function of temperature. In accordance with previous measurements, the Josephson current IJ is reduced at low temperature in small high-resistance tunnel junctions. Smaller deviations in IJ from theoretical estimates can be explained by strong coupling effects.