Vortex states of Bi2Sr2CaCu2O8+y with antidot array probed by c-axis transport measurements

To study the vortex states in Bi2Sr2CaCu2O8+y (Bi2212) high-Tc superconductor with periodic array of antidots, we have measured the c-axis critical current in a stack of the intrinsic Josephson junctions with a square lattice of antidots, which gives us information on the c-axis correlation of the pancake vortices. Without the antidot array, the c-axis critical current can probe the first-order vortex lattice melting transition. Additionally, a suppression of the critical current in the vicinity of zero magnetic field is found, which may be related to the instability of vortex lattice under the parallel current flow. With the square lattice of antidots, enhancements of the critical current due to the matching effect are observed in both the integer and fractional matching fields. By mapping the critical current on H-T diagram, the influence of the matching effect on the phase boundary of vortex solid and liquid is shown.