Dynamics of driven vortices in the presence of a regular array of columnar defects

The effects of pinning by a square lattice of columnar defects (CD) on the low-temperature dynamics of vortex lines driven by a uniform force, F-d, oriented in the (1,0) CD-lattice direction, are investigated by Langevin dynamics simulations of a London, model for straight vortex lines interacting with CD of radius comparable to the vortex-core radius, Starting the simulations with the vortex lines in the zero-drive ground-state, it is found that for F-d much greater than F-p (F-p = single CD pinning force) reordering into a new state occurs. The spa tial order in this state is identified with that of the ground-state of stationary vortex lines interacting with the potential obtained by averaging the vortex-line CD-lattice interaction in the direction of motion. The dynamical phase diagram is investigated by starting the simulations from, this ground-state and with F-d much greater than F-p, and progressively decreasing F-d, Evidence is reported for the existence of two dynamical phases: high-drive elastic flow, and low-drive plastic flow, These are characterized by studying the behavior of the vortex lines density-density correlation function, and velocity distribution as a function of F-d.