Dynamics of magnetic flux lines in the presence of correlated disorder

We investigate the dynamics of interacting magnetic flux lines driven by an external current in the presence of linear pinning centers, arranged either in a periodic square lattice or placed randomly in space, by means of three-dimensional Monte Carlo simulations. Compared to the non-interacting case, the repulsive forces between the vortices reduce the critical current J_c, as determined from the depinning threshold in the current-voltage (I-V) characteristics. Near the depinning current J_c, the voltage power spectrum S(w) reveals broad-band noise, characterized by a $1/wa$ power law decay with a <= 2. At larger currents the flux lines move with an average velocity v_{cm}. For a periodic arrangement of columnar pins with a lattice constant $d$ and just above J_c, distinct peaks appear in the voltage noise spectrum S(w) at w ~ v_{cm}/d which we interpret as the signature of stick-slip flux line motion.