LANGEVIN DYNAMICS SIMULATION OF VORTICES IN A LAYERED SUPERCONDUCTOR

We study the dynamics of the vortex lattice with a Langevin dynamics m ethod in a layered superconductor, for systems of up to 4180 vortices, subject to periodic boundary conditions. The interaction between the pancake vortices in each layer is of magnetic origin, and the accompan ying long-range interaction is dealt with exactly. Temperature is take n into account by means of a gaussian noise source. Depending on the v alue of the magnetic field (applied perpendicular to the layers) we ob serve layer decoupling prior to lattice melting. We calculate the temp erature dependence of the positional and angular correlation functions , and several time dependent correlation functions. The obtained resul ts are compared to simulations for a single layer. Some effects of pin ning are addressed briefly. In the simulations, we also obtain the NMR spin-relaxation rates due to thermal motion of the vortices. The rele vance of this relaxation mechanism for existing systems is discussed, and the effects of weak pinning on the melting are addressed briefly.