Vortex washboard voltage noise in type-II superconductors |
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Authors: | T J Bullard J Das G L Daquila and U C T?uber |
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Institution: | (1) Department of Physics and Center for Stochastic Processes and Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0435, USA;(2) U.S. Air Force, Wright-Patterson Air Force Base, OH 45433-5648, USA;(3) Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA |
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Abstract: | 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 bythe
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 uniquefeatures that depend characteristically on the type
of material defects presentin the sample. |
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Keywords: | PACS" target="_blank">PACS 74 25 Qt Vortex lattices flux pinning flux creep 74 25 Sv Critical currents 74 40 +k Fluctuations (noise chaos nonequilibrium superconductivity localization etc ) |
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