11 research outputs found
Aging and scaling laws in -hydroquinone-clathrate
The dielectric permittivity of the orientational glass
methanol(x=0.73)--hydroquinone-clathrate has been studied as function of
temperature and waiting time using different temperature-time-protocols. We
study aging, rejuvenation and memory effects in the glassy phase and discuss
similarities and differences to aging in spin-glasses. We argue that the
diluted methanol-clathrate, although conceptually close to its magnetic
pendants, takes an intermediate character between a true spin-glass and a pure
random field system
Aging in KLiTa0: a domain growth interpretation
The aging behaviour of the a.c. susceptibility of randomly substituted
KLiTa0 crystals reveals marked differences with spin-glasses in
that cooling rate effects are very important. The response to temperature steps
(including temperature cycles) was carefully studied. A model based on
thermally activated domain growth accounts for all the experimental results,
provided one allows for a large distribution of pinning energies, in such a way
that `slow' and `fast' domains coexist. Interesting similarities with deeply
supercooled liquids are underlined.Comment: 4 pages. Preprint LPTENS/9820, submitted to Phys. Rev. Let
Aging and memory effects in beta-hydrochinone-clathrate
The out-of-equilibrium low-frequency complex susceptibility of the
orientational glass methanol(73%)-beta-hydrochinone-clathrate is studied using
temperature-stop protocols in aging experiments . Although the material does
not have a sharp glass transition aging effects including rejuvenation and
memory are found at low temperatures. However, they turn out to be much weaker,
however, than in conventional magnetic spin glasses.Comment: 5 pages RevTeX, 6 eps-figures include
Memory Effects in Granular Material
We present a combined experimental and theoretical study of memory effects in
vibration-induced compaction of granular materials. In particular, the response
of the system to an abrupt change in shaking intensity is measured. At short
times after the perturbation a granular analog of aging in glasses is observed.
Using a simple two-state model, we are able to explain this short-time
response.
We also discuss the possibility for the system to obey an approximate
pseudo-fluctuation-dissipation theorem relationship and relate our work to
earlier experimental and theoretical studies of the problem.Comment: 5 pages, 4 figures, reference list change
Mean-field theory of temperature cycling experiments in spin-glasses
We study analytically the effect of temperature cyclings in mean-field
spin-glasses. In accordance with real experiments, we obtain a strong
reinitialization of the dynamics on decreasing the temperature combined with
memory effects when the original high temperature is restored. The same
calculation applied to mean-field models of structural glasses shows no such
reinitialization, again in accordance with experiments. In this context, we
derive some relations between experimentally accessible quantities and propose
new experimental protocols. Finally, we briefly discuss the effect of field
cyclings during isothermal aging.Comment: Some misprints corrected, references updated, final version to apper
in PR
Domain growth by isothermal aging in 3d Ising and Heisenberg spin glasses
Non-equilibrium dynamics of three dimensional model spin glasses - the Ising
system FeMnTiO and the Heisenberg like system Ag(11 at%
Mn) - has been investigated by measurements of the isothermal time decay of the
low frequency ac-susceptibility after a quench from the paramagnetic to the
spin glass phase. It is found that the relaxation data measured at different
temperatures can be scaled according to predictions from the droplet scaling
model, provided that critical fluctuations are accounted for in the analyzes.Comment: 5 pages, 3 figure
Glassy systems under time-dependent driving forces: application to slow granular rheology
We study the dynamics of a glassy model with infinite range interactions
externally driven by an oscillatory force. We find a well-defined transition in
the (Temperature-Amplitude-Frequency) phase diagram between (i) a `glassy'
state characterized by the slow relaxation of one-time quantities, aging in
two-time quantities and a modification of the equilibrium
fluctuation-dissipation relation; and (ii) a `liquid' state with a finite
relaxation time. In the glassy phase, the degrees of freedom governing the slow
relaxation are thermalized to an effective temperature. Using Monte-Carlo
simulations, we investigate the effect of trapping regions in phase space on
the driven dynamics. We find that it alternates between periods of rapid motion
and periods of trapping. These results confirm the strong analogies between the
slow granular rheology and the dynamics of glasses. They also provide a
theoretical underpinning to earlier attempts to present a thermodynamic
description of moderately driven granular materials.Comment: Version accepted for publication - Physical Review
Subwavelength anti-diffracting beams propagating over more than 1,000 Rayleigh lengths
Propagating light beams with widths down to and below the optical wavelength require bulky large-aperture lenses and remain focused only for micrometric distances. Here, we report the observation of light beams that violate this localization/depth- of-focus law by shrinking as they propagate, allowing resolution to be maintained and increased over macroscopic propagation lengths. In nanodisordered ferroelectrics we observe a non-paraxial propagation of a sub-micrometre-sized beam for over 1,000 diffraction lengths, the narrowest visible beam reported to date. This unprecedented effect is caused by the nonlinear response of a dipolar glass, which transforms the leading opticalwave equation into a Klein-Gordon-type equation that describes a massive particle field. Our findings open the way to high-resolution optics over large depths of focus, and a route to merging bulk optics into nanodevices