Vortex dynamics in superconducting films with twin boundary networks

We present two-dimensional computer simulation results of magnetic vortex systems driven by Lorentz force through polycrystalline superconductors with random network structures of twin boundaries. Langevin dynamics simulations of a point vortex model demonstrate that (1) the threshold behavior of I-V curves is observed, (2) the threshold current is a decreasing function of an average superconducting grain size, and (3) the 1/f noise power spectrum of the ensemble-averaged vortex velocity appears near the threshold current