Vortex lens in Bi2Sr2CaCu2O8+y

The control of pancake vortices (PVs) caused by Josephson vortices (JVs) is demonstrated in the highly anisotropic superconductor Bi2Sr2CaCu2O8+(y). The moderately strong attractive interactions between PVs and JVs in the crossing-lattices state under tilted fields are utilized to change the distribution of PVs. Micro-Hall probe magnetometry and differential magneto-optical imaging provide direct evidence for such a novel control. We have succeeded in visualizing the lensing effect of PVs by slowly ramping the in-plane field in the presence of a small c-axis field. How the lensing effect is affected by the history, the density of PVs, and the temperature is systematically studied.