Effects of first-order vortex phase transition on the electronic states of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y}

Abstract

We measured the complex surface impedance Zs= Rs+iXsof optimally- and over-doped Bi2Sr2CaCu2Oysingle crystals around the vortex-phase boundaries. In both doping states, the surface reactance Xsincreased rapidly just above the first-order melting transition field and the so-called second magnetization peak field, while no obvious anomalies were observed in the surface resistance Rs. From the analysis of the relationship between Xsand Rs, we showed that the origin of this anomaly is not the loss of pinning but the reduction of the superfluid density above the transition.