Experimental investigation of dislocation sources in the fluxon lattice of a type-II superconductor

Abstract

This paper presents experimental evidence for the presence of dislocation sources in the fluxon lattice threading a type-II superconductor in the mixed state. The possibility of dislocation sources in the fluxon lattice is of interest because their presence may considerably reduce the critical current of the superconductor.

The alternating voltage observed in our experiments when a small a.c. current superimposed on a small direct current is passed through a sample is interpreted as due to the presence of sections of fluxon-lattice dislocation pinned at each end. The alternating current causes the dislocation sections to vibrate, and the direct current bows out the vibrating section. This interpretation is confirmed by additional experiments on a mechanical analogue model. The pinned sections of fluxon-lattice dislocation could act as dislocation sources analogous to Frank—Bead sources.