Collective resonance modes of Josephson vortices in a sandwiched stack of Bi2Sr2CaCu2O8+x intrinsic Josephson junctions

Abstract

We observed splitting of the low-bias vortex-flow branch in a dense-Josephson-vortex state into multiple subbranches in current-voltage characteristics of Bi2Sr2CaCu2O8+x intrinsic Josephson junctions in the long-junction limit. Each subbranch corresponds to a plasma mode in serially coupled Josephson junctions. Splitting into low-bias linear subbranches with a spread in the slopes and the intersubbranch mode-switching character are in good quantitative agreement with the prediction of the weak but finite interjunction capacitive-coupling model incorporated with the inductive coupling.