Fluxon motion in the stacked intrinsic Josephson junctions in Bi2Sr2CaCu2Oy single crystals

The fluxon motion excited by external microwaves has been investigated in naturally stacked, intrinsic Josephson junctions of Bi2Sr2CaCu2Oy single crystals. For mesa-shaped single-crystals in cavity resonant modes, either odd or even order subharmonic steps, in addition to fundamental steps, caused by the phase-locked oscillation of a coupled multifluxon have been successfully observed in the current-voltage characteristics, depending on the frequency of the microwaves. For mesa-shaped and as-grown single-crystals in off-resonant modes, only fundamental steps caused by the one-way flow of such a multifluxon have been observed.