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(307) Production(s) de BERTHIER L.


Role of fluctuations in the yielding transition of twodimensional glasses
Auteur(s): Ozawa M., Berthier L., Biroli Giulio, Tarjus Gilles
(Article) Publié:
Physical Review Research, vol. p.023203 (2020)
Texte intégral en Openaccess :
Ref HAL: hal02880608_v1
Ref Arxiv: 1912.06021
DOI: 10.1103/PhysRevResearch.2.023203
Ref. & Cit.: NASA ADS
Exporter : BibTex  endNote
Résumé: We numerically study yielding in twodimensional glasses which are generated with a very wide range of stabilities by swap MonteCarlo simulations and then slowly deformed at zero temperature. We provide strong numerical evidence that stable glasses yield via a nonequilibrium discontinuous transition in the thermodynamic limit. A critical point separates this brittle yielding from the ductile one observed in less stable glasses. We find that twodimensional glasses yield similarly to their threedimensional counterparts but display larger sampletosample disorderinduced fluctuations, stronger finitesize effects, and rougher spatial wandering of the observed shear bands. These findings strongly constrain effective theories of yielding.



Lowfrequency vibrations of jammed packings in large spatial dimensions
Auteur(s): Shimada Masanari, Mizuno Hideyuki, Berthier L., Ikeda A.
(Article) Publié:
Physical Review E: Statistical, Nonlinear, And Soft Matter Physics, vol. p.052906 (2020)
Texte intégral en Openaccess :
Ref HAL: hal02880594_v1
Ref Arxiv: 1910.07238
DOI: 10.1103/PhysRevE.101.052906
Ref. & Cit.: NASA ADS
Exporter : BibTex  endNote
Résumé: Amorphous packings prepared in the vicinity of the jamming transition play a central role in theoretical studies of the vibrational spectrum of glasses. Two meanfield theories predict that the vibrational density of states $g(\omega)$ obeys a characteristic power law, $g(\omega)\sim\omega^2$, called the nonDebye scaling in the lowfrequency region. Numerical studies have however reported that this scaling breaks down at low frequencies, due to finite dimensional effects. In this study, we prepare amorphous packings of up to $128000$ particles in spatial dimensions from $d=3$ to $d=9$ to characterise the range of validity of the nonDebye scaling. Our numerical results suggest that the nonDebye scaling is obeyed down to a frequency that gradually decreases as $d$ increases, and possibly vanishes for large $d$, in agreement with meanfield predictions. We also show that the prestress is an efficient control parameter to quantitatively compare packings across different spatial dimensions.



Glass stability changes the nature of yielding under oscillatory shear
Auteur(s): Yeh Weiting, Ozawa M., Miyazaki Kunimasa, Kawasaki T., Berthier L.
(Article) Publié:
Physical Review Letters, vol. 124 p.225502 (2020)
Texte intégral en Openaccess :
Ref HAL: hal02880587_v1
Ref Arxiv: 1911.12951
DOI: 10.1103/PhysRevLett.124.225502
Ref. & Cit.: NASA ADS
Exporter : BibTex  endNote
Résumé: We perform molecular dynamics simulations to investigate the effect of a glass preparation on its yielding transition under oscillatory shear. We use swap Monte Carlo to investigate a broad range of glass stabilities from poorly annealed to highly stable systems. We observe a qualitative change in the nature of yielding, which evolves from ductile to brittle as glass stability increases. Our results disentangle the relative role of mechanical and thermal annealing on the mechanical properties of amorphous solids, which is relevant for various experimental situations from the rheology of soft materials to fatigue failure in metallic glasses.



Depletion of TwoLevel Systems in Ultrastable ComputerGenerated Glasses
Auteur(s): Khomenko Dmytro, Scalliet C., Berthier L., Reichman David, Zamponi Francesco
(Article) Publié:
Physical Review Letters, vol. 124 p. (2020)
Texte intégral en Openaccess :
Ref HAL: hal02738157_v1
Ref Arxiv: 1910.11168
DOI: 10.1103/PhysRevLett.124.225901
WoS: 000537199500009
Ref. & Cit.: NASA ADS
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9 Citations
Résumé: Amorphous solids exhibit quasiuniversal lowtemperature anomalies whose origin has been ascribed to localized tunneling defects. Using an advanced Monte Carlo procedure, we createin silicoglasses spanning from hyperquenched to ultrastable glasses. Using a multidimensional pathfinding protocol, we locate tunneling defects with energy splittings smaller than kBTQ, with TQ the temperature below which quantum effects are relevant (TQ≈1 K in most experiments). We find thatas the stability of a glass increases, its energy landscape as well as the manner in which it is probed tend to deplete the density of tunneling defects, as observed in recent experiments. We explore therealspace nature of tunneling defects, and find that they are mostly localized to a few atoms, butare occasionally dramatically delocalized



Universal relaxation dynamics of sphere packings below jamming
Auteur(s): Ikeda A., Kawasaki T., Berthier L., Saitoh Kuniyasu, Hatano Takahiro
(Article) Publié:
Physical Review Letters, vol. p.058001 (2020)
Texte intégral en Openaccess :
Ref HAL: hal02591059_v1
Ref Arxiv: 1904.07359
DOI: 10.1103/PhysRevLett.124.058001
WoS: 000510750600010
Ref. & Cit.: NASA ADS
Exporter : BibTex  endNote
2 Citations
Résumé: We show that nonBrownian suspensions of repulsive spheres below jamming display a slow relaxational dynamics with a characteristic time scale that diverges at jamming. This slow time scale is fully encoded in the structure of the unjammed packing and can be readily measured via the vibrational density of states. We show that the corresponding dynamic critical exponent is the same for randomly generated and sheared packings. Our results show that a wide variety of physical situations, from suspension rheology to algorithmic studies of the jamming transition are controlled by a unique diverging timescale, with a universal critical exponent.



Brittle yielding of amorphous solids at finite shear rates
Auteur(s): Singh M., Ozawa M., Berthier L.
(Article) Publié:
Physical Review Materials, vol. 4 p.025603 (2020)
Texte intégral en Openaccess :
Ref HAL: hal02569130_v1
Ref Arxiv: 1912.06416
DOI: 10.1103/PhysRevMaterials.4.025603
WoS: 000515722500007
Ref. & Cit.: NASA ADS
Exporter : BibTex  endNote
Résumé: Amorphous solids display a ductile to brittle transition as the kinetic stability of the quiescent glass is increased, which leads to a material failure controlled by the sudden emergence of a macroscopic shear band in quasistatic protocols. We numerically study how finite deformation rates influence ductile and brittle yielding behaviors using model glasses in two and three spatial dimensions. We find that a finite shear rate systematically enhances the stress overshoot of poorlyannealed systems, without necessarily producing shear bands. For wellannealed systems, the nonequilibrium discontinuous yielding transition is smeared out by finite shear rates and it is accompanied by the emergence of multiple shear bands that have been also reported in metallic glass experiments. We show that the typical size of the bands and the distance between them increases algebraically with the inverse shear rate. We provide a dynamic scaling argument for the corresponding lengthscale, based on the competition between the deformation rate and the propagation time of the shear bands.



A localization transition underlies the modecoupling crossover of glasses
Auteur(s): Coslovich D., Ninarello A. S., Berthier L.
(Article) Publié:
Scipost Physics, vol. p.77 (2019)
Texte intégral en Openaccess :
Ref HAL: hal02445176_v1
Ref Arxiv: 1811.03171
DOI: 10.21468/SciPostPhys.7.6.077
WoS: 000505803200006
Ref. & Cit.: NASA ADS
Exporter : BibTex  endNote
4 Citations
Résumé: We study the equilibrium statistical properties of the potential energy landscape of several glass models in a temperature regime so far inaccessible to computer simulations. We show that unstable modes of the stationary points undergo a localization transition in real space close to the modecoupling crossover temperature determined from the dynamics. The concentration of localized unstable modes found at low temperature is a nonuniversal, finite dimensional feature not captured by meanfield glass theory. Our analysis reconciles, and considerably expands, previous conflicting numerical results and provides a characteristic temperature for glassy dynamics that unambiguously locates the modecoupling crossover.
