Vortex states in Bi2Sr2CaCu2O8+y single crystals with various configurations of artificial defects

To study the influence of artificial hole defects on the vortex matter in high-Tc superconductors, we have measured electrical transport properties in the vortex state of Bi2Sr2CaCu2O8+y (Bi2212) single-crystal thin films which have hole configurations with different symmetries. In samples with a square hole array, the flow resistance of pancake vortices exhibits dips at multiples of the matching fields, while it is absent in a random hole configuration. Such matching effect occurs even in a vortex liquid phase, suggesting that the periodicity in hole configuration fabricated induces in-plane order in vortex-liquid flow.