617 research outputs found
Local order and crystallization of dense polydisperse hard spheres
No full textThis dataset is associated with "Local order and crystallization of dense polydisperse hard spheres", Daniele Coslovich, Misaki Ozawa, and Ludovic Berthier, J. Phys.: Condens. Matter 30, 144004 (2018) [doi:10.1088/1361-648X/aab0c9 arXiv:1801.09638].
It include scripts and data files to allow for the replication of the figures. EPS figures were generated using gnuplot version 5.0.</p
Hyperuniform Interfaces in Nonequilibrium Phase Coexistence
No full textWe show that long-wavelength interfacial fluctuations are strongly suppressed in nonequilibrium phase coexistence between bulk hyperuniform systems. Using simulations of three distinct microscopic models, we demonstrate that hyperuniform interfaces are much smoother than equilibrium ones, with a universal reduction of height fluctuations at large scale. We derive a nonequilibrium interface equation from the field theory of the bulk order parameter, and predict a reduction in height fluctuations, Sh(k)≡⟨|h(k)|2⟩∼|k|-1, in stark contrast to equilibrium capillary wave theory where Sh(k)∼|k|-2. Our results establish a new universality class for nonequilibrium interfaces, highlighting the fundamental role of suppressed bulk fluctuations in shaping interfacial dynamics far from equilibrium
Scaling the glassy dynamics of active particles: Tunable fragility and reentrance
No full textUnderstanding the influence of activity on dense amorphous assemblies is crucial for biological processes such as wound healing, embryogenesis, or cancer progression. Here, we study the effect of self-propulsion forces of amplitude [Formula: see text] and persistence time [Formula: see text] in dense assemblies of soft repulsive particles by simulating a model particle system that interpolates between particulate active matter and biological tissues. We identify the fluid and glass phases of the three-dimensional phase diagram obtained by varying [Formula: see text], [Formula: see text], and the packing fraction [Formula: see text]. The morphology of the phase diagram accounts for a nonmonotonic evolution of the relaxation time with [Formula: see text], which is a direct consequence of the crossover in the dominant relaxation mechanism, from glassy to jamming. A second major consequence is the evolution of the glassy dynamics from sub-Arrhenius to super-Arrhenius. We show that this tunable glass fragility extends to active systems analogous observations reported for passive particles. This analogy allows us to apply a dynamic scaling analysis proposed for the passive case, in order to account for our results for active systems. Finally, we discuss similarities and differences between our results and recent findings in the context of computational models of biological tissues
Bypassing sluggishness: SWAP algorithm and glassiness in high dimensions
No full textRéf Journal: Phys. Rev. E 99, 031301 (2019)International audienceThe recent implementation of a swap Monte Carlo algorithm (SWAP) for polydisperse mixtures fully bypasses computational sluggishness and closes the gap between experimental and simulation timescales in physical dimensions and . Here, we consider suitably optimized systems in , to obtain insights into the performance and underlying physics of SWAP. We show that the speedup obtained decays rapidly with increasing the dimension. SWAP nonetheless delays systematically the onset of the activated dynamics by an amount that remains finite in the limit . This shows that the glassy dynamics in high dimensions is now computationally accessible using SWAP, thus opening the door for the systematic consideration of finite-dimensional deviations from the mean-field description
A random walk description of the heterogeneous glassy dynamics of attracting colloids
No full textWe study the heterogeneous dynamics of attractive colloidal particles close to the gel transition using confocal microscopy experiments combined with a theoretical statistical analysis. We focus on single particle dynamics and show that the self-part of the van Hove distribution function is not the Gaussian expected for a Fickian process, but that it reflects instead the existence, at any given time, of colloids with widely different mobilities. Our confocal microscopy measurements can be described well by a simple analytical model based on a conventional continuous time random walk picture, as already found for several other glassy materials. In particular, the theory successfully accounts for the presence of broad tails in the van Hove distributions that exhibit exponential, rather than Gaussian, decay at large distance
A localization transition underlies the mode-coupling crossover of glasses
No full textThis dataset is associated to "A localization transition underlies the mode-coupling crossover of glasses" by D. Coslovich, A. Ninarello and L. Berthier [https://arxiv.org/abs/1811.03171].
It includes post-processed data and workflow to reproduce the analysis and the figures of the article and of the supplemental information.
The easiest way to reproduce the analysis and figures, and then check the results, is to use the make script:
./make all
Alternatively, the analysis and figures can be reproduced in any of the following ways
following the workflow described in the org-mode project file project.org
using the individual bash and gnuplot scripts in src/ and plots/
Folders and files description:
analysis/: post-processed data
src/: bash, python and gnuplot scripts needed to reproduce the analysis
plots/: eps figures that appear in the paper and supplemental information and associated gnuplot scripts
make: convenience script to setup the python environment, analyze the data and reproduce the figures
project.org: org-mode project file with workflow and supplemental information
project.pdf: pdf version of the org-mode project file
project.bib: bibtex bibliography associated to the project
Dependencies:
numpy (1.16.3)
argh (0.26.2)
atooms (1.9.1)
gnuplot (5.0.0)
The analysis scripts have been tested with python versions 2.7 and 3.5. The org-mode project file has been tested with org version 9.1.13.
Note: this dataset does not contain (at least yet) the particle configurations associated to saddle points, only the post-processed files containing selected properties of their normal modes.
Changelog:
1.0.0
initial submission
1.1.0
add "all" target to ./make
fix ./make check
improve setup description
</ul
Exploring the jamming transition over a wide range of critical densities
No full textWe numerically study the jamming transition of frictionless
polydisperse spheres in three dimensions. We use an efficient
thermalisation algorithm for the equilibrium hard sphere fluid and
generate amorphous jammed packings over a range of critical jamming
densities that is about three times broader than in previous studies.
This allows us to reexamine a wide range of structural properties
characterizing the jamming transition. Both isostaticity and the
critical behavior of the pair correlation function hold over the entire
range of jamming densities. At intermediate length scales, we find a
weak, smooth increase of bond orientational order. By contrast,
distorted icosahedral structures grow rapidly with increasing the volume
fraction in both fluid and jammed states. Surprisingly, at large scale
we observe that denser jammed states show stronger deviations from
hyperuniformity, suggesting that the enhanced amorphous ordering
inherited from the equilibrium fluid competes with, rather than
enhances, hyperuniformity. Finally, finite size fluctuations of the
critical jamming density are considerably suppressed in the denser
jammed states, indicating an important change in the topography of the
potential energy landscape. By considerably stretching the amplitude of
the critical “J-line”, our work disentangles physical properties at the
contact scale that are associated with jamming criticality, from those
occurring at larger length scales, which have a different nature.</jats:p
Out of equilibrium dynamics of magnetic monopoles in spin ice
No full textLes glaces de spin, comme Dy2Ti2O7 et Ho2Ti2O7, sont des matériaux présentant un magnétisme particulièrement exotique. Ils constituent les premiers composés cristallins ferromagnétiques frustrés à avoir été découverts. Cette frustration permet la fractionnalisation des degrés de liberté de spin et l’émergence de monopôles magné-tiques, dont la physique est formalisée par le modèle des haltères.Dans cette thèse, nous étudions dans un premier temps le diagramme de phase de ce modèle grâce à un parallèle avec le modèle de Blume-Capel S = 2. On identifie dans ce diagramme la phase fragmentée observée expérimentalement dans Ho2Ir2O7,et on localise le point critique de la transition entre la phase glace de spin et la phase fragmentée.Dans un second temps, on montre numériquement que la dynamique du système autour de ce point critique appartient à la classe d’universalité du modèle d’Ising 3D. On utilise pour cela deux outils : les lois d’échelle de Kibble-Zurek et le rapport de fluctuation-dissipation. L’obtention de ce dernier a nécessité l’introduction d’une méthode novatrice pour le calcul des fonctions de réponse. Nous soulignons également que ces outils sont spécifiquement intéressants dans le cas des glaces de spin où les temps microscopiques sont de l’ordre de 1 μs, rendant le ralentissement critique observable expérimentalement.Dans un troisième temps, nous employons à nouveau la violation du théorème de fluctuation-dissipation pour caractériser un régime fortement hors équilibre de la phase glace de spin, où les degrés de liberté sont cinétiquement bloqués du fait de l’attraction coulombienne entre les monopôles.Spin ices, such as Dy2Ti2O7 and Ho2Ti2O7, are materials exhibiting exotic magnetic properties. They were the first frustrated ferromagnetic crystalline compounds to be discovered. The frustration leads to the fractionnalisation of the spin degrees of freedom and the emergence of magnetic monopoles, whose physics is formalised in the dumbbell model. In this thesis, we study the full phase diagram of this model in analogy with theS=2 Blume-Capel model. We identify in this diagram the fragmented phase observed experimentally in Ho2Ir2O7, and we localise the critical point of the transition between the spin ice phase and the fragmented phase.In a second part, we show numerically that the dynamics of this system at thecritical point belongs to the 3D Ising university class. We use for this two tools :the Kibble-Zurek scaling law and the fluctuation-dissipation ratio. For the latter, ithas been necessary to introduce a novel method to measure response functions. Wealso emphasize that these tools are specifically interesting for spin ice materials, as the unusually long microscopic time scale (1 μs) should make it possible to experimentallyobserve out-of-equilibrium phenomena related to critical slowing down.In a third part, we use the violation of the fluctuation-dissipation theorem to characterise a strongly out-of-equilibrium regime of spin ice - a thermal quench from high to low temperature, where degrees of freedom are kinetically blocked because ofthe Coulombic attraction between the monopoles
Solides amorphes de la transition vitreuse à 1 Kelvin
No full textComprendre la nature fondamentale de la transition vitreuse et des solides amorphes est au cœur d’un vaste effort de recherche. La description théorique des solides vitreux reste essentielle- ment phénoménologique. Ce travail explore l’hypothèse selon laquelle une nouvelle phase amorphe de la matière expliquerait naturellement leurs propriétés physiques. Nous analysons la thermodynamique des verres dans la limite de dimension infinie. Cette théorie exacte de champ moyen prédit deux phases vitreuses, une "simple" et une "marginalement stable", séparées par une transition de Gardner. Nous démontrons que les verres sont marginalement stables dans une grande variété de conditions physiques, couvrant des régimes pertinents pour décrire la matière granulaire, les mousses, les émulsions, les colloïdes durs et mous, ainsi que les verres moléculaires. Nous confrontons nos prédictions théoriques à des simulations numériques en trois dimensions. Nous développons un algorithme numérique efficace qui crée des verres très stables. Nous montrons que les verres colloïdaux et granulaires sont marginalement stables: ils évoluent dans un paysage hiérarchique et présentent des excitations délocalisées de basse énergie. Dans ce régime, des variations cycliques de la température donnent lieu à des effets de rajeunissement et de mémoire, précédemment observés dans les verres de spin. En revanche, le comportement des verres moléculaires est régi par des défauts localisés, dont les propriétés quantiques à basse température sont également analysées. Nous étudions le rôle de l’entropie configurationnelle dans le ralentissement dynamique qui accompagne la formation du verre. Nous mesurons l’entropie configurationnelle dans des liquides à très basse température, et analysons les théories thermodynamiques de la transition vitreuse.Understanding the fundamental nature of the glass transition and amorphous solids is at the core of a large research effort. The theoretical description of glassy solids remains mainly phe- nomenological. This work explores the hypothesis that a new amorphous phase of matter naturally explains their physical properties. We analyze the thermodynamics of glasses in the limit of large dimensions. This exact mean-field theory predicts two glassy phases, ‘simple’ and ‘marginally stable’, separated by a Gardner transition. We find that glasses are marginally stable in a wide range of physical conditions, covering regimes relevant to describe granular matter, foams, emul- sions, hard and soft colloids, and molecular glasses. We confront our theoretical predictions to three-dimensional numerical simulations. We develop an efficient numerical scheme which creates well-relaxed glasses. Colloidal and granular glasses are found to be marginally stable: they evolve in a hierarchical landscape, and present delocalized low-lying excitations. Temperature cycles in this regime give rise to rejuvenation and memory effects, previously observed in spin glasses. In contrast, the behavior of molecular glasses is governed by localized two level systems, whose low- temperature tunneling properties are also analyzed. We investigate the role of the configurational entropy in the glassy dynamical slowdown accompanying glass formation. We measure the config- urational entropy in extremely supercooled liquids, and assess thermodynamic theories of the glass transition
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