Flux-line entanglement as the mechanism of melting transition in high-temperature superconductors in a magnetic field

The mechanism of the flux-line-lattice (FLL) melting in anisotropic high-T-c, superconductors in B parallel to (c) over cap is clarified by Monte Carlo simulations of the three-dimensional frustrated XY model. The percentage of entangled flux lines abruptly changes at the melting temperature T-m, while no sharp change can be found in the number and size distribution of vortex loops around T-m. Therefore, the origin of this melting transition is the entanglement of flux lines. Scaling behaviors of physical quantities are consistent with the above mechanism of the FLL melting. The Lindemann number is also evaluated without any phenomenological arguments. [S0163-1829(99)50818-7].