DYNAMIC BEHAVIOR OF JOSEPHSON-COUPLED LAYERED STRUCTURES

We have investigated Josephson effects in stacks of both artificial an d natural Josephson junctions. The measurements have been performed on Nb/Al-AlO(x)/Nb multilayers and on small single crystals of Bi2Sr2CaC u2O8. Both systems exhibit multiple branched I-V characteristics in ze ro magnetic field. In finite magnetic fields coupling via currents flo wing along the superconducting layers is essential, since the layers a re thinner than the London penetration depth. All observations are in good agreement with numerical simulations of stacks of coupled Josephs on junctions. These simulations predict that a large number of junctio ns can be phase locked in large magnetic fields via Fiske resonances e xcited in all junctions.