Collective Josephson vortex dynamics in a finite number of intrinsic Josephson junctions

TL;DR

This study experimentally confirms the collective transverse plasma modes excited by Josephson vortex lattices in intrinsic Josephson junctions of Bi2Sr2CaCu2O8+x, revealing vortex configurations and lattice dynamics through current-voltage analysis.

Contribution

First experimental observation of collective Josephson vortex lattice modes and their temperature and magnetic field dependence in intrinsic junction stacks.

Findings

Observation of magnetoresistance oscillations indicating triangular vortex lattice.

Detection of multiple sub-branches in current-voltage characteristics representing different vortex modes.

Identification of a transition from triangular to rectangular vortex lattice configurations.

Abstract

We report the experimental confirmation of the collective transverse plasma modes excited by the Josephson vortex lattice in stacks of intrinsic Josephson junctions in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$ single crystals. The excitation was confirmed by analyzing the temperature ($T$) and magnetic field ($H$) dependencies of the multiple sub-branches in the Josephson-vortex-flow region of the current-voltage characteristics of the system. In the near-static Josephson vortex state for a low tunneling bias current, pronounced magnetoresistance oscillations were observed, which represented a triangular-lattice vortex configuration along the c axis. In the dynamic vortex state in a sufficiently high magnetic field and for a high bias current, splitting of a single Josephson vortex-flow branch into multiple sub-branches was observed. Detailed examination of the sub-branches for varying $H$ field reveals that sub-branches represent the different modes of the Josephson-vortex lattice along the c axis, with varied configuration from a triangular to a rectangular lattices. These multiple sub-branches merge to a single curve at a characteristic temperature, above which no dynamical structural transitions of the Josephson vortex lattice is expected.