Dislocation assemblies exhibit a jamming or yielding transition at a critical external shear stress value $σ=σ_c$. Nevertheless the nature of this transition has not been ascertained. Here we study the heterogeneous and collective nature of dislocation dynamics within a crystal plasticity model close to $σ_c$, by considering the first-passage properties of the dislocation dynamics. As the transition is approached in the moving phase, the first passage time distribution exhibits scaling, and a related peak {\it dynamical} susceptibility $χ_4^*$ diverges as $χ_4^* \sim (σ-σ_c)^{-α}$, with $α\approx 1.1$. We relate this scaling to an avalanche description of the dynamics. While the static structural correlations are found to be independent of the external stress, we identify a diverging dynamical correlation length $ξ_y$ in the direction perpendicular to the dislocation glide motion.
Collective motion of dislocations is governed by the obstacles they encounter. In pure crystals, dislocations form complex structures as they become jammed by their anisotropic shear stress fields. On the other hand, introducing disorder to the crystal causes dislocations to pin to these impeding elements and, thus, leads to a competition between dislocation-dislocation and dislocation-disorder interactions. Previous studies have shown that, depending on the dominating interaction, the mechanical response and the way the crystal yields change. Here we employ three-dimensional discrete dislocat…
Alloying metals with other elements is often done to improve the material strength or hardness. A key microscopic mechanism is precipitation hardening, where precipitates impede dislocation motion, but the role of such obstacles in determining the nature of collective dislocation dynamics remains to be understood. Here, three-dimensional discrete dislocation dynamics simulations of FCC single crystals are performed with fully coherent spherical precipitates from zero precipitate density upto $ρ_p = 10^{21}\,\text{m}^{-3}$ and at various dislocation-precipitate interaction strengths. When the d…
Active work measures how far the local self-forcing of active particles translates into real motion. Using Population Monte Carlo methods, we investigate large deviations in the active work for repulsive active Brownian disks. Minimizing the active work generically results in dynamical arrest; in contrast, despite the lack of aligning interactions, trajectories of high active work correspond to a collectively moving, aligned state. We use heuristic and analytic arguments to explain the origin of dynamical phase transitions separating the arrested, typical, and aligned regimes.
Like other critical phenomena, the jamming transition accompanies the divergence of the relaxation time $τ$. A recent numerical study of frictionless spherical particles proves that $τ$ is inversely proportional to the lowest non-zero eigenvalue $λ_1$ of the dynamical matrix. In this note, we derive the scaling of $λ_1$ below the jamming transition point $φ_J$ by solving the linearized dynamical equation. The resultant critical exponent agrees with a previous theoretical result for sheared suspension obtained by applying the virtual work theorem to a simple shear, highlighting the universality…
Dynamical fluctuations close to Jamming versus Vibrational Modes : a pedagogical discussion illustrated on hard spheres simulations, colloidal and granular experiments
On the universality of jamming percolation: reply to the comment of Jeng and Schwarz
In Phys. Rev. Lett. 96，035702（2006）中，我们介绍了一类显示动态玻璃化转变的动力学约束模型。我们集中讨论了一个特殊的例子：“骑士”模型。正如Jeng和Schwarz cond-mat/0612484正确指出的那样，我们忽略了骑士模型的一些额外的定向冻结结构，这些结构不是简单的定向渗流（DP）路径：这些“更厚”的定向结构降低了临界密度。在这里，我们认为，尽管如此，全定向过程是在DP普适性类和T-结之间的垂直段这些引起了干扰渗流过渡与我们以前的工作中讨论的普遍性质。此外，我们提出了其他模型，我们以前的所有结果，包括临界密度的值，严格举行。
A dynamical relation between dual finite temperature classical and zero temperature quantum systems: quantum critical jamming and quantum dynamical heterogeneities
Anomalous Criticality of Absorbing State Transition toward Jamming
National Laboratory of Solid State Microstructures, Nanjing University（南京大学固体微结构物理国家重点实验室）；Collaborative Innovation Center of Advanced Microstructures and School of Physics, Nanjing University（南京大学先进微结构协同创新中心及物理学院）
Jamming is a phenomenon shared by a wide variety of systems, such as granular materials, foams, and glasses in their high density regime. This has motivated the development of a theoretical framework capable of explaining many of their static critical properties with a unified approach. However the dynamics occurring in the vicinity of the jamming point has received little attention and the problem of finding a connection with the local structure of the configuration remains unexplored. Here we address this issue by constructing physically well defined structural variables using the informatio…
Gradient descent dynamics in complex energy landscapes, i.e. featuring multiple minima, finds application in many different problems, from soft matter to machine learning. Here, we analyze one of the simplest examples, namely that of soft repulsive particles in the limit of infinite spatial dimension $d$. The gradient descent dynamics then displays a jamming transition: at low density, it reaches zero-energy states in which particles' overlaps are fully eliminated, while at high density the energy remains finite and overlaps persist. At the transition, the dynamics becomes critical. In the $d\…
A dilute suspension of active Brownian particles in a dense compressible viscoelastic fluid, forms a natural setting to study the emergence of nonreciprocity during a dynamical phase transition. At these densities, the transport of active particles is strongly influenced by the passive medium and shows a dynamical jamming transition as a function of activity and medium density. In the process, the compressible medium is actively churned up -for low activity, the active particle gets self-trapped in a spherical cavity of its own making, while for large activity, the active particle ploughs thro…
Recent numerical studies have identified the persistence time of active motion as a critical parameter governing glassy dynamics in dense active matter. Here we studied dynamics in liquids of granular active ellipsoids with tunable persistence and velocity. We show that increasing the persistence time at moderate supercooling is equivalent to increasing the strength of attraction in equilibrium liquids and results in reentrant dynamics not just in the translational degrees of freedom, as anticipated, but also in the orientational ones. However, at high densities, motile topological defects, un…
