Cherenkov Instability of Driven Vortices in a Stack of Intrinsic Josephson Junctions

We investigated stability of flux flow of parallel vortices in a layered superconductor modeled by a stack of coupled Josephson junctions with parameters characteristic of BSCCO crystals. Our numerical simulations of vortices propagating along coupled layers have shown that, once a vortex reaches a critical velocity, it triggers a cascade of vortex-antivortex pairs which form a dissipative domain expanding both along and across the layers and ultimately driving the entire stack into a resistive state. This effect caused by a critical wake of Cherenkov radiation behind moving vortices is most pronounced in underdamped junctions at low temperatures for which the instability occurs at a threshold current density J_s well below the Josephson critical current density of the interlayer junctions. Here J_s(H) decreases as the density of vortices increases. In the resistive state at J>J_s standing electromagnetic modes are generated in a stack of layers with open edges, or propagating waves are generated in a stack of annular Josephson junctions.