Josephson lattice structure in mesoscopic intrinsic Josephson junctions by means of flux-flow resistance in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$

TL;DR

This study investigates the dynamical behavior of Josephson vortices in Bi2212, revealing a transition from triangular to square lattice structures under varying magnetic fields through flux-flow resistance oscillations.

Contribution

It provides experimental evidence of Josephson vortex lattice structure transitions in mesoscopic intrinsic Josephson junctions using flux-flow resistance measurements.

Findings

Flux-flow resistance oscillates periodically with magnetic field.

Transition from triangular to square vortex lattice observed.

Edge deformation influences vortex lattice structure.

Abstract

Dynamical nature of the Josephson vortex (JV) system in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212) has been investigated in the presence of the c-axis current with magnetic field alignments very close to the $ab$-plane. As a function of magnetic fields, the c-axis JV flux flow resistance oscillates periodically in accordance with the proposed JV triangular structure. We observe that this oscillating period becomes doubled above a certain field, indicating the structure transition from triangle to square structure. This transition field becomes lower in junctions with smaller width perpendicular to the external field. We interpret that this phenomena as the effect of the edge deformation of the JV lattice due to surface current of intrinsic Josephson junctions as pointed by Koshelev.