Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session V05: Disordered and Glassy Systems (Non-Polymeric)Live
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Sponsoring Units: DSOFT Chair: Yoav Lahini, Tel Aviv University Room: 05 |
Thursday, March 18, 2021 3:00PM - 3:12PM Live |
V05.00001: Why phonon scattering in glasses is universally small at low temperatures Herve M. Carruzzo, Clare Yu We present a novel view of the standard model of tunneling two level systems (TLS) to explain the puzzling universal value of a quantity, C ~ 3 x 10-4, that characterizes phonon scattering in glasses below 1 K as reflected in thermal conductivity, ultrasonic attenuation, internal friction, and the change in sound velocity. Physical considerations lead to a broad distribution of phonon-TLS couplings that (1) exponentially renormalize tunneling matrix elements, and (2) reduce the TLS density of states through TLS-TLS interactions. We find good agreement between theory and experiment for a variety of individual glasses. |
Thursday, March 18, 2021 3:12PM - 3:24PM Live |
V05.00002: Transport and Elastic Properties of Dispersions of Hard Particles at Jamming Murray Skolnick, Salvatore Torquato We generate a spectrum of dense jammed packings of hard particles with varying degrees of order using the Adaptive Shrinking Cell (ASC) optimization scheme. Of particular interest are maximally random jammed (MRJ) packings, which are both prototypical glasses (simultaneously mechanically rigid and maximally disordered) and hyperuniform. Disordered hyperuniform materials can exhibit novel optical, transport and mechanical properties. We treat our generated jammed packings as dispersions of particles embedded in a matrix phase. The effective diffusion characteristics, effective dielectric constant, and effective elastic moduli of our jammed dispersions are estimated using rigorous bounding techniques as well as computer simulation techniques. |
Thursday, March 18, 2021 3:24PM - 3:36PM Live |
V05.00003: Avalanche statistics at the yielding transition of amorphous solids: universality in elastoplastic models Ezequiel E Ferrero I focus on the statistics of avalanches produced by the characteristic stick-slip behavior close to the yielding transition in the deformation of amorphous materials, enquiring into its common properties among different elasto-plastic models (EPMs) [1]. |
Thursday, March 18, 2021 3:36PM - 3:48PM Live |
V05.00004: Correlated crackling and avalanches during slow relaxation of crumpled sheets Yaniv Friedman, Yoav Lahini Crumpling a thin sheet of elastic material such as Mylar into a three dimensional structure results in the formation of a soft metamaterial with unusual, glass-like mechanical properties such as logarithmic relaxation or Kovacs-like memory effect. |
Thursday, March 18, 2021 3:48PM - 4:00PM Live |
V05.00005: Stability and Degrees of Freedom Varda Faghir Hagh, Eric Corwin, M Lisa Manning, Andrea Liu, Sidney Robert Nagel Recent advances in both the jamming and glass communities have led to the development of new protocols that can create particularly stable solids. Such systems, whether they be physical systems created using vapor-deposition or numerical systems created using the SWAP or breathing algorithms, exist in exceptionally deep energy minima that are marked by the absence of low-frequency modes. We introduce new protocols for creating stable jammed packings that work by first introducing and then subsequently removing degrees of freedom such as particle size or interparticle stiffness. We find that different choices for the degrees of freedom can lead to very different gains in the stability of the packing. At least in one case, those degrees of freedom that can push a system to much deeper energy minima are also the ones responsible for the rigidity transition itself. |
Thursday, March 18, 2021 4:00PM - 4:12PM Live |
V05.00006: Visualizing Gardner-like effects in the transition from transient to persistent contacts in experiments on granular crystals. Lars Kool, Patrick Charbonneau, Karen Daniels Recent numerical studies of granular materials suggest that the persistence of inter-particle contacts during cyclic loading depends on the lowest packing fraction (φ) to which they are decompressed. Contacts are transient at low φ, and increasingly conserved beyond a threshold φG. We present an experimental study of the conservation of particle contacts as a function of φ, for a nearly perfect bi-disperse granular crystal of photo-elastic discs. Particles were levitated by an air-cushion to limit basal friction, and agitated from compressed air streams to simulate thermal noise. Using auto-correlations in the force chain network (formed after compression beyond jamming) as a measure of particle contact conservation, we found marked transition from transient to conserved contacts. Moreover, we showed that this transition coincides with the onset of Gardner-like physics in amorphous solids. |
Thursday, March 18, 2021 4:12PM - 4:24PM Live |
V05.00007: Singularities in Hessian element distributions of amorphous media Vishnu V. Krishnan, Smarajit Karmakar, Kabir Ramola We show that the distribution of elements H in the Hessian matrices associated with amorphous materials exhibit singularities P(H) ∼ |H|γ with an exponent γ < 0, as |H| → 0. We utilize the rotational invariance of amorphous structures to derive these exponents exactly for systems with particles interacting via radially symmetric, pairwise potentials. We show that γ depends only on the degree of smoothness at cutoff of the interaction potential, independent of other details of interaction, and is identical in both two and three dimensions. We verify our predictions with numerical simulations of models of structural glass formers. Finally, we show that such singularities affect the vibrational properties of amorphous solids, through the distributions of the minimum eigenvalue of the Hessian matrix. Crucially, short-ranged interaction models display a novel, universal, non-debye regime in the density of states. |
Thursday, March 18, 2021 4:24PM - 4:36PM Live |
V05.00008: Impacts of bi-layered elastic projectiles Christophe D'ANGELO, Franck Celestini, Christophe Raufaste In contact mechanics the study of the impact with a substrate remains a challenge for heterogeneous systems, from clusters of particles at the microscopic level [1] to the collisions of macroscopic vehicles [2]. We investigate experimentally the impact of a bi-layered elastic projectile with a substrate. Our projectiles are made of a soft part on top of a rigid one. Velocities before and after the impact are measured to characterize the coefficient of restitution (Cor). |
Thursday, March 18, 2021 4:36PM - 4:48PM Live |
V05.00009: Measuring Structure and Dynamics of Nanoparticle Surfactant Assemblies at Liquid-Liquid Interfaces Zachary Fink, Paul Y Kim, Qingteng Zhang, Suresh Narayanan, Shaul Aloni, David Hoagland, Thomas Russell While many techniques can assess the packing of nanoparticle (NP, D<50 nm) assemblies, such as GISAXS, AFM, and super resolution spectroscopies, they have drawbacks when obtaining dynamics data, as film damage, imaging time, and fluorescent quenching make reliable measurements difficult. The interfacial assembly of NP surfactants (NPS), oppositely charged carboxylated NPs and aminated surfactants, greatly increase NP binding energies and provide a unique platform to overcome these impediments. We used in-situ GI-XPCS, SAXS, and liquid cell TEM (LTEM) to probe the packing and dynamics of NPS assemblies as a function of areal density. XPCS data show Bragg peak formation and assembly transition from a liquid-like phase to a solid film with much longer in-plane relaxation times as jamming progresses. To augment XPCS results we are developing an LTEM approach to directly observe the spatial and temporal NP rearrangements in real time using a step emulsification flow cell. By controlling the molecular aspects that govern NPS interactions in jammed environments, we have elucidated the kinetics and dynamics of the assemblies. |
Thursday, March 18, 2021 4:48PM - 5:00PM Live |
V05.00010: Internal Loss in Sticky Crumpled Matter Andrew Croll, Theresa M Elder, Wathsala Jayawardana There has recently been a surge of interest aimed towards understanding the load bearing ability of randomly confined thin films (crumpled matter). Advances have been made; notably, the discovery that adhesion plays a major role in setting the magnitude of the compressive strength of a crumple. In this work we explore the details of this relation in greater depth, through confocal microscopy and compression testing of thin, sticky, crumpled polymer films. Specifically, we explore the dynamics of compression as a means of unraveling the mechanisms of adhesion within the structures. |
Thursday, March 18, 2021 5:00PM - 5:12PM Live |
V05.00011: Characterizing Individual Shear Defects in Colloidal Glasses Aidan Duncan, Zsolt Terdik, Ilya Svetlizky, Agnese Curatolo, Michael Brenner, Frans A Spaepen, Katharine Jensen Although the mechanisms governing plastic deformation in crystals have been well-understood for decades, we lack an equivalent depth of understanding for amorphous materials. Colloidal glass provides a unique experimental system with which to study the structure, defects, and dynamics of a generic amorphous material. We analyze particle-level trajectories and local strain fields obtained from experiments on ~1-μm-diameter, hard-sphere colloidal glasses under conditions of uniform shear. We directly identify individual “shear defects” or “shear transformation zones” (STZs) as they are activated in the glass, by cross-correlating the measured local strain field with that predicted for Eshelby inclusions. By fitting for both the STZ location and size, it is possible to identify the specific particles that comprise an individual STZ and directly determine how their free volume, local density, coordination, and other structural predictors evolve leading up to and after the shear transformation. |
Thursday, March 18, 2021 5:12PM - 5:24PM On Demand |
V05.00012: Avalanche statistics of a moving contact line Caishan YAN, Dongshi Guan, Yin Wang, Pik-Yin Lai, Hsuan-Yi Chen, Penger Tong Many disordered systems show crackling noise when driven by an external force or filed, such as Barkhausen noise in magnetization of ferromagnetic materials, acoustic emission in plastic deformation and seismic activity in earthquakes. An important feature of these noises is the power law distribution of avalanche sizes, implying a universal mechanism underlying the avalanche dynamics in these systems. Here we report avalanche statistics of a moving contact line (CL) formed on a vertical hanging fiber, which is driven through a liquid-air interface by an atomic-force-microscope (AFM) cantilever. The measured capillary force exerted on the circular CL intersecting the liquid-air interface exhibits zig-zag-like fluctuations, indicating a stick-slip motion of the CL. In the stick state, the capillary force increases linearly with the CL displacement. Once the capillary force reaches its local maximal value Fc, the CL slips in the form of avalanches, accompanied by a loss of capillary force δf. The measured δf is found to follow a power-law distribution, as predicted by the ABBM model. The experimental results provide new insights into the avalanche dynamics of CLs, which may also help to understand other avalanche phenomena. |
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