Microwave Response of Bi₂Sr₂CaCu₂O_8+δ Surface Intrinsic Josephson Junctions with Bending Pancake Vortices

We study the microwave response of surface intrinsic Josephson junctions on Bi₂Sr₂CaCu₂O_8+δ, in which bending pancake vortex lines are introduced in a controllable way. It is found that the bending vortices can greatly influence the response. In some cases, typical Shapiro steps that lie far above the quasiparticle branch are observed, with the step interval satisfying the Josephson relation and their amplitude versus the square root of microwave power following the Bessel function behaviour. In the other cases, current steps that lie on the quasiparticle branch are observed, but only one or two steps appear at the same time under the variation of the microwave power.