5 research outputs found
Vortex Washboard Voltage Noise in Type-II Superconductors
In order to characterize flux flow through disordered type-II
superconductors, we investigate the effects of columnar and point defects on
the vortex velocity / voltage power spectrum in the driven non-equilibrium
steady state. We employ three-dimensional Metropolis Monte Carlo simulations to
measure relevant physical observables including the force-velocity /
current-voltage (I-V) characteristics, vortex spatial arrangement and structure
factor, and mean flux line radius of gyration. Our simulation results compare
well to earlier findings and physical intuition. We focus specifically on the
voltage noise power spectra in conjunction with the vortex structure factor in
the presence of weak columnar and point pinning centers. We investigate the
vortex washboard noise peak and associated higher harmonics, and show that the
intensity ratios of the washboard harmonics are determined by the strength of
the material defects rather than the type of pins present. Through varying
columnar defect lengths and pinning strengths as well as magnetic flux density
we further explore the effect of the material defects on vortex transport. It
is demonstrated that the radius of gyration displays quantitatively unique
features that depend characteristically on the type of material defects present
in the sample.Comment: Latex, 17 pages, 14 figure
Slow relaxation and aging kinetics for the driven lattice gas
We numerically investigate the long-time behavior of the density-density
auto-correlation function in driven lattice gases with particle exclusion and
periodic boundary conditions in one, two, and three dimensions using precise
Monte Carlo simulations. In the one-dimensional asymmetric exclusion process on
a ring with half the lattice sites occupied, we find that correlations induce
extremely slow relaxation to the asymptotic power law decay. We compare the
crossover functions obtained from our simulations with various analytic results
in the literature, and analyze the characteristic oscillations that occur in
finite systems away from half-filling. As expected, in three dimensions
correlations are weak and consequently the mean-field description is adequate.
We also investigate the relaxation towards the nonequilibrium steady state in
the two-time density-density auto-correlations, starting from strongly
correlated initial conditions. We obtain simple aging scaling behavior in one,
two, and three dimensions, with the expected power laws.Comment: 12 pages, 18 figures; to appear in Phys. Rev. E (2011