Collective resonance modes of Josephson vortices in sandwiched stack of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$ intrinsic Josephson junctions

摘要

We observed splitting of the low-bias vortex-flow branch in adense-Josephson-vortex state into multiple sub-branches in current-voltagecharacteristics of intrinsic Josephson junctions (IJJs) ofBi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$ single crystals in the long-junction limit.Each sub-branch corresponds to a plasma mode in serially coupled Josephsonjunctions. Splitting into low-bias linear sub-branches with a spread in theslopes and the inter-sub-branch mode-switching character are in goodquantitative agreement with the prediction of the weak but finiteinter-junction capacitive-coupling model incorporated with the inductivecoupling. This suggests the importance of the role of the capacitive couplingin accurately describing the vortex dynamics in serially stacked IJJs.