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

TL;DR

This study reveals how collective plasma modes influence vortex dynamics in stacked intrinsic Josephson junctions of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$, highlighting the significance of capacitive coupling in these systems.

Contribution

It demonstrates the observation of multiple plasma modes in vortex-flow states and confirms the role of capacitive coupling in modeling Josephson vortex dynamics.

Findings

Splitting of vortex-flow branch into multiple sub-branches observed.

Sub-branches correspond to plasma modes in coupled junctions.

Quantitative agreement with capacitive-coupling model.

Abstract

We observed splitting of the low-bias vortex-flow branch in a dense-Josephson-vortex state into multiple sub-branches in current-voltage characteristics of intrinsic Josephson junctions (IJJs) of Bi$_{2}$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 Josephson junctions. Splitting into low-bias linear sub-branches with a spread in the slopes and the inter-sub-branch mode-switching character are in good quantitative agreement with the prediction of the weak but finite inter-junction capacitive-coupling model incorporated with the inductive coupling. This suggests the importance of the role of the capacitive coupling in accurately describing the vortex dynamics in serially stacked IJJs.