DAMPING EFFECT ON THE RADIO-FREQUENCY INDUCED VOLTAGE STEPS IN A JOSEPHSON TUNNEL JUNCTION

The phase-lock stability of a Josephson tunnel junction to the external rf frequency (ω1) is the most important feature of the Josephson voltage standard. The junction plasma frequency (ωP) should be much lower than ω1 to avoid any chaotic instability. But we found that the moderate junction damping can support the phase-lock stability so that a larger step size reaching the Bessel function values can be achieved even in the region where ωP≃ω1. Measurements of a moderately damped tunnel junction confirm the simulation results.© 1995 American Institute of Physics.