Collective oscillations of the superconducting gap of multilayered Josephson junctions

Collective modes involving the gap amplitude Δ and phase Φ in a multilayered superconducting junction are considered. The junction is formed by a sequence of "clean" superconducting layers S separated by insulating barriers I. Using the quasiclassical Green function method, we derive the self-consistent linear equations describing the collective amplitude δ and phase φ oscillations. We find that the δ and φ modes in "clean" multilayered Josephson junctions may be long lived for a range of magnitudes of the barrier transparency and Cooper coupling strength. We find that the frequency of the resonances in a multilayered junction can be tuned by applying a bias supercurrent across the adjacent subjunction.