Inter-layer phase difference and flux-line entanglement at first-order melting transition of high- Tc vortex systems

Abstract

The mechanism of the flux-line-lattice melting in high- T c superconductors is investigated numerically. The percentage of entangled flux lines abruptly increases at the melting temperature T m, which indicates that this excitation is the origin of the melting transition. The one-dimensional size dependence of T m ensures this picture. The inter-layer phase difference sharply jumps at T m, which is consistent with the Josephson plasma resonance experiment. This jump is scaled by the anisotropy constant and the flux-line density for a wide range of parameters. For extremely large anisotropy, this jump saturates and becomes as large as those observed experimentally.