Possible formation of rectangular Josephson-vortex lattice in narrow Bi-2212 intrinsic Josephson junctions by the enhanced edge effect

Josephson vortex lattice in narrow Bi-2212 intrinsic Josephson junctions have been studied. Formation of rectangular Josephson vortex lattice is expected in narrow width due to the edge effect. Current-voltage (I-V) characteristics were measured as a function of the magnetic field applied parallel to their a-b planes. Maximum zero bias current (IC,branch) and flux-flow voltage were measured. We observed that the IC,branch monotonically decreased with magnetic field up to 0.6 T. Above 0.6 T, IC,branch showed an enhancement, accompanied by an enhancement of flux-flow voltage thus flux-flow speed, up to 1.0 T. This result indicates a change in the configuration of vortex lattices from triangular to other structure (possibly rectangular) by the edge effect in which configuration both the flux-flow voltage and IC,branch are enhanced due to an increase in the maximum velocity of the vortex lattice.