“universal” Resistance Jump of Vortices at the Melting Transition

The subject of vortex dynamics in high Tc superconductors is of topical interest [1,2]. In recent years, new aspects of the phase diagram of the vortex lattice have been elucidated through experiment. Perhaps one of the salient recent experimental findings is the first order melting transition of the vortex lattice, first observed in transport measurements [3] and later confirmed in a number of equilibrium properties [4]. It is now well accepted that in clean BiSrCuO and in untwined YBaCuO samples the melting transition of the vortex lattice for an applied magnetic field parallel to the c-axis is first order and that the superconducting coherence is simultaneously lost in all directions at the melting temperature. A striking regularity is observed in the transport experiments: for different values of the applied magnetic field, which is proportional to the areal density of vortices, the in-plane resistivity pt,h( T ) decreases with decreasing temperature until it jumps (essentially) discontinuously to zero at the melting temperature TI, , with pu/,( T l l ) independent of field. Moreover, recent studies of the melting transition in YBaCuO show that the jump in the out-of-plane resistivity p c is also field independent. The resistance due to vortex motion is given by