Vortex lattice melting induced by force-free current in Bi2Sr2CaCu2O8+y

To investigate the melting transition of the vortex lattice under a force-free current parallel to the c axis, we have measured the field dependence of c-axis resistance, critical current, and I-V characteristics in vortex states of Bi(2)Sr(2)CaCu(2)O(8+y) single crystals. The melting transition field H(m) observed in the critical current measurements was almost 20% smaller than H(m) determined by the resistance measurements. Furthermore, it was found that H(m) is reduced as the parallel current increases by measurements of the differential resistance with various bias currents. We have first demonstrated to induce the vortex-lattice melting transition by the force-free current. Although monotonical decrease of H(m) with increasing current is consistent with the theoretical expectations, the whole behavior of the current dependence of H(m) does not obey them.