Bloch vortices in one-dimensional Josephson junction arrays

Abstract

The quantum dynamics of vortices in very long and narrow arrays of Josephson junctions have been studied experimentally. The motion of the vortices through the one-dimensional array is homologous to the motion of a boson through a one-dimensional periodic potential. The external force on the vortices is proportional to the bias current. When the bias current exceeds a critical value, a negative differential resistance is observed. In the presence of external RF radiation the IV-characteristic exhibits steps at currents which scale with the RF frequency. The position of the steps also depends on the vortex density, which is probably caused by a collective effect of the vortices. These preliminary results strongly indicate the existence of a vortex bandstructure.