Correlation lengths, disorder, and dynamics of vortex matter as heard through the noise
Rabin, Michael William
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/30848
Description
Title
Correlation lengths, disorder, and dynamics of vortex matter as heard through the noise
Author(s)
Rabin, Michael William
Issue Date
1998
Doctoral Committee Chair(s)
Weissman, Michael B.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
correlation lengths
disorder
dynamics
vortex matter
noise
type II superconductor
2H-NbSe₂
Language
en
Abstract
I have conducted a series of experiments measuring flux-flow voltage noise in the type II
superconductor 2H-NbSe₂ concentrating on the dynamics and possible phase transitions of vortex
matter associated with the peak-effect. I emphasize five conclusions: (1) Traditional models of
vortex dynamics relying on purely dynamical correlations, rigid bundles, or simple two-state
channel flow are invalid in the peak regime of2H-NbSe₂. (2) The noise reflects vortex
configurations present in the pinned state, and our methods probe the static correlations among
the vortices in the pinned state. (3) The broad-band noise is sensitive to extremely small AC
magnetic field perturbations (at ~ 100 Hz); δH/H~ 10⁻⁵ can reduce the noise power at 1 Hz by a
factor of2. This sensitivity of the broad-band noise reflects a loss of configurational memory,
which is directly related to a correlation length (Ln) in the static vortex solid. Near the onset of
the peak (at Hpl), Ln rapidly reaches an apparent sample-size limit as H decreases, suggesting a
continuous phase transition or length-scale crossover in the vortex solid associated with the onset
of the peak effect. (4) In the narrow range of fields around the noise maximizing field, the
fluctuation kinetics are completely different from those at lower and higher H, indicating the
inhomogeneous nucleation of a new phase. (5) The remarkable behavior under various types of
AC driving implies low-dimensional, deterministic, periodic dynamics during periods when the
Lorentz force is zero. For this work, I used the automated, digital synthesis of periodic
cancellation signals based on the synchronized sampling of the periodic residual voltage. I
invented this technique to automate the exploration of parameter space associated with AC noise
measurement.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
