Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session L24: Jamming, Criticality, and the Gardner TransitionFocus
|
Hide Abstracts |
Sponsoring Units: GSNP DSOFT Chair: Corey O'Hern, Yale University Room: 401 |
Wednesday, March 4, 2020 8:00AM - 8:36AM |
L24.00001: Pressure-dependent shear response of jammed packings of frictionless, spherical particles Invited Speaker: Kyle VanderWerf The mechanical response of packings of purely repulsive, spherical particles to athermal, quasistatic simple shear near jamming onset is highly nonlinear. Previous studies have shown that, at small pressure p, the ensemble-averaged static shear modulus <G-G0> scales with pα, where α ≈ 1, but above a characteristic pressure p**, <G-G0> scales with pβ, where β ≈ 0.5. However, we find that the shear modulus Gi for an individual packing typically decreases linearly with p along a geometrical family where the contact network does not change. We resolve this discrepancy by showing that, while the shear modulus does decrease linearly within geometrical families, <G> also depends on a contribution from discontinuous jumps in Gi that occur at the transitions between geometrical families. For p > p**, geometrical-family and rearrangement contributions to <G> are of opposite signs and remain comparable for all system sizes. <G> can be described by a scaling function that smoothly transitions between two power-law exponents α and β. We also demonstrate the phenomenon of compression unjamming, where a jammed packing unjams via isotropic compression. |
Wednesday, March 4, 2020 8:36AM - 8:48AM |
L24.00002: Gardner physics in three-dimensional structural glasses Camille Scalliet, Ludovic Berthier, Francesco Zamponi The discovery of Gardner phases in structural glasses has profound consequences for their physical behavior, e.g. elasticity, rheology, low-temperature transport. It is therefore crucial to understand which type of materials, and under which physical conditions, are in the Gardner phase. Based on mean-field results [1], we present a comprehensive numerical study of 3d glasses. By changing external parameters, we explore regimes relevant to granular, colloidal, and molecular glasses. We delimit two separate regimes. We find that glasses close enough to jamming present a hierarchical landscape [2], and rejuvenation and memory effects expected in a Gardner phase [3]. In the regime far from jamming, relevant to atomic glasses, no Gardner physics is observed. Our study reveals instead the presence of localised excitations, whose role in low-temperature transport is analyzed. Our results suggest that Gardner physics should be observed in colloidal and non-Brownian particles near jamming. |
Wednesday, March 4, 2020 8:48AM - 9:00AM |
L24.00003: Dimensional Dependence of Scaling Prefactors in Overjammed Systems James Sartor, Eric Corwin Granular materials express universal properties regardless of the material properties of the individual grains. This universality of granular packings is a direct consequence of the statistics of contact forces between grains. When packing fraction changes, material properties are governed by the creation and destruction of new contacts. The number of excess contacts, packing fraction, and pressure all characterize distance to the jamming transition and are related by scaling theory made possible by the universality of granular materials. While the scalings between these parameters follow simple power laws, the prefactors to these scalings are not universal. We present measurements of these prefactors in dimensions 2-10. These prefactors depend nontrivially on dimension and differ from the asymptotic high dimensional values predicted by mean field theory. |
Wednesday, March 4, 2020 9:00AM - 9:12AM |
L24.00004: Vibrational Properties of Hard and Soft Spheres are Unified at Jamming Francesco Arceri, Eric Corwin Glasses and granular materials are characterized by the appearance of amorphous rigidity at the jamming point. While grains described as soft spheres jam in the limit of zero pressure, in a thermal hard sphere glass jamming is only achieved at infinite pressure when all the available space is filled and particles are in enduring contact with one another. The criticality near jamming has been largely explored from the soft side of the transition both in theory and numerics. The study of the vibrational properties in hard spheres has proven to be challenging to measure numerically because no analytic interaction is defined. Recently, an effective interaction between hard spheres at zero temperature has been proposed, of which minimization is able to produce typical configurations of low temperature colloidal glasses. This protocol ensures a proper definition of the vibrational spectrum near and at jamming. We observe a variety of low frequency modes which, for a certain range of density, agree with those found in jammed soft spheres. Therefore, the vibrational properties of hard and soft spheres near jamming are fully governed by the geometry of the system and the critical point represents a smooth joining between the two descriptions. |
Wednesday, March 4, 2020 9:12AM - 9:24AM |
L24.00005: Effect of annealing on the nature of the yielding transition of amorphous solids Srikanth Sastry, Himangsu Bhaumik, Giuseppe Foffi Recently it has been demonstrated employing athermal quasi-static cyclic shear that an atomistic model glass former exhibits a sharp yielding transition across a sharply defined critical amplitude [1], which is further characterized by strain localization at the post yield regime [2], and the attainment of low energy structures approaching the yielding point. Here, we study the applicability of these results to a model of silica, and further, study the effect of annealing on the nature of yielding in both the model systems. We analyse the manner in which the discontinuous nature of the transition changes with annealing and compare our results with recent results analysing the effect of annealing in glasses [4]. |
Wednesday, March 4, 2020 9:24AM - 9:36AM |
L24.00006: Universal non-mean-field scaling in the density of states of amorphous solids Harukuni Ikeda Amorphous solids have excess soft modes in addition to the phonon modes described by the Debye theory. Recent numerical results show that if the phonon modes are carefully removed, the density of state of the excess soft modes exhibit universal quartic scaling, independent of the interaction potential, preparation protocol, and spatial dimensions. We hereby provide a theoretical framework to describe this universal scaling behavior. For this purpose, we extend the mean-field theory to include the effects of finite-dimensional fluctuation. Based on a semiphenomenological argument, we show that mean-field quadratic scaling is replaced by the quartic scaling in finite dimensions. Furthermore, we apply our formalism to explain the pressure and protocol dependence of the excess soft modes. |
Wednesday, March 4, 2020 9:36AM - 9:48AM |
L24.00007: A jamming plane of sphere packings Yuliang Jin, Hajime Yoshino The concept of jamming has attracted great research interest due to its broad relevance in soft matter such as liquids, glasses, colloids, foams, and granular materials, and its deep connection to the sphere packing problem and phase transitions. Here we show numerically that the phase space of frictionlessly jammed states can be extended from the well-known jamming-point along the density axis to a jamming plane spanned by the density and shear-strain axes,. We discuss how this jamming plane can be explored by standard athermal and thermal jamming protocols, and relate the protocol-dependence of the explored phase space to the reversibility of the routes to the jammed states. While all jammed states are isostatic and in the same universality class, their anisotropies and amorphous orders depend on the density and the shear strain. Among all points on the jamming plane, the jamming-point is special: it sets a sharp lower bound in the thermodynamic limit for the jamming density of all frictionless random packings, and the configurations there have the minimum amorphous order. |
Wednesday, March 4, 2020 9:48AM - 10:00AM |
L24.00008: Out-of-equilibrium jamming of liquids and glasses: memory and criticality Peter Morse, Patrick Charbonneau The emergence of memory in glass-forming liquids has recently been described by mean-field theory. Liquids equilibrated below the onset packing fraction (or above the onset temperature) share the same set of inherent states, while on the other side of that onset the set of inherent states depends on the equilibrated liquid properties. The resulting jammed states then have memory of the original liquid. In this talk, we present a new method to jam hard sphere liquids efficiently, which enables us to reliably detect this onset and relate its value with the mean-field prediction. This jamming algorithm also exhibits a signature of an out-of-equilibrium Gardner transition, corresponding to the point at which the roughness of the optimization landscape becomes algorithmically notable. Taken together these results will help inform a theory of out-of-equilibrium liquids and glasses. |
Wednesday, March 4, 2020 10:00AM - 10:12AM |
L24.00009: Creating ultra-stable jammed packings by training on pressure Varda Faghir Hagh, Eric Corwin, M. Lisa Manning, Andrea Jo-Wei Liu, Sidney Robert Nagel Disordered materials are highly trainable because of their rugged energy landscapes. The idea of training is to evolve the physical properties of the microscopic constituents in a given system until a macroscopic state with desired emergent properties is achieved. Here, we train packings of soft harmonic spheres based on their per-particle pressures. First, the pressure on each particle is measured and then the radius of each particle is changed proportional to the inverse of its pressure, (i.e. particles with larger pressure get slightly smaller and particles with smaller pressure grow slightly larger). This process is repeated iteratively until pressure fluctuations disappear from the system. The final trained packings have a much lower energy and are mechanically ultra-stable regardless of original (untrained) packings' distance from the instability. This training process moves the critical packing fraction to a higher value and engraves a memory of training in the system that does not disappear under decompression. |
Wednesday, March 4, 2020 10:12AM - 10:24AM |
L24.00010: Intruder dynamics in granular flow Scott Newlon, Leo Silbert The dynamics and kinematics of a single intruder particle in two dimensional, disordered packings of frictionless bidisperse discs interacting through linear and non-linear contact forces are investigated using computer simulations. To initiate motion of the intruder requires a threshold force to be exceeded which depends on the pressure of the packing. Beyond this critical force, for a given driving force, the average intruder velocity scales with the excess driving force. The velocity curves for different pressures are found to obey an universal scaling relation that depends on the initial packing pressure. We also find that the critical, threshold force is related to the shear modulus, thereby connecting the microrheological properties of the intruder at the grain scale to the bulk, macroscopic mechanical properties of the packing. |
Wednesday, March 4, 2020 10:24AM - 10:36AM |
L24.00011: One-step replica-symmetry-breaking phase in low-dimensional spin glasses Judith Hoeller, Nicholas Read It is long known that mean-field theory of an Ising spin glass predicts a second-order phase boundary in the temperature–magnetic field plane between a paramagnet and a replica-symmetry-breaking phase. Here, we show that at nonzero magnetic fields and just above six dimensions, this phase diagram is modified by the appearance of a one-step replica symmetry-breaking phase below the transition, and a tricritical point beyond which the transition becomes quasi-first-order. These results may explain the reported absence of a diverging correlation length in the presence of a magnetic field in less-than-six-dimensional spin glasses in simulations and high-temperature series expansions. |
Wednesday, March 4, 2020 10:36AM - 10:48AM |
L24.00012: Origin of Two-Step Glass Transition in 2D Colloidal Suspension of Rods Xinzhuo Liu, Huaguang Wang, Zexin Zhang, Xinsheng Ling We report an experimental study of monolayers of colloidal rods which exhibits a two-step glass transition with no appearance of nematic domains. Instead, it was found that rods tend to align with each other randomly in two preferred configurations, parallel, or perpendicular. We argue that the bi-modal distribution of the relative angles of the rods in the glassy phase is due to the existence of an activation barrier separating two local free energy minima in the configurational space. This barrier increases significantly when the first transition is approached, thereby freezing out the rotational motion while the translational motion remains diffusive. The results suggest that the activation barrier for rods rotating relative to each other is the key to the two-step glass transition. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700