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

摘要

Dynamical nature of the Josephson vortex (JV) system inBi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212) has been investigated in thepresence 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 flowresistance oscillates periodically in accordance with the proposed JVtriangular structure. We observe that this oscillating period becomes doubledabove a certain field, indicating the structure transition from triangle tosquare structure. This transition field becomes lower in junctions with smallerwidth perpendicular to the external field. We interpret that this phenomena asthe effect of the edge deformation of the JV lattice due to surface current ofintrinsic Josephson junctions as pointed by Koshelev.