Competition between lensing and dome formation of vortices in Bi2Sr2CaCu2O8+y

The vortex lensing effect in the crossing-lattices state of Bi2Sr2CaCu2O8+y is studied as a function of the sweep rate of the in-plane field (Hx) using the differential magneto-optical technique. The one-dimensional vortex lensing observed at high sweep rate of Hx changes into the two-dimensional vortex dome as the sweep rate is reduced. However, it turns out that the vortex dome is still present when we observe the one-dimensional lensing in the differential image at the high sweep rate of Hx. The apparent disappearance of the vortex dome in such conditions is found to be due to the ineffectiveness of Josephson vortices’ motion to the vortex dome when they move too fast.