Two-dimensional resonant modes in stacked Josephson junctions

In a vertical stack of Josephson junctions, vortices in adjacent junctions are coupled by screening currents if the electrodes are thinner than the London penetration depth. We investigate typical junction parameters of both niobium multilayers and intrinsic Josephson junctions in high-Tc single crystals. Using coupled one-dimensional sine-Gordon equations, stable coherent motion of Josephson vortices in an external magnetic field is predicted. This motion is triggered by two-dimensional resonances of the stack. For the resonance frequencies and amplitudes analytical expressions are derived.