Creep in yield stress materials advances through scale-free avalanches*

Amorphous solids exit the elastic regime and undergo the yielding transition when driven at their flow stress. At the critical stress and zero temperature, such systems exhibit scale-free avalanches, a pseudogap in the distribution of local stabilities, and are characterized by a robust set of nontrivial critical exponents.  Thermal activations alter this picture, gapping the stability distribution and truncating the size of mechanical avalanches [1,2].  Below the flow stress, thermally activated amorphous solids exhibit creep. Recent experiments with crumpled sheets show that creep in this system advances through very slow, self-similar, ‘thermal’ avalanches [3]. Using a mesoscale elastoplastic model (EPM) with an Arrhenius activation rule, we find good agreement with experimental data and a beautiful example of self-organized criticality. With a finite-size scaling analysis, we characterize the static and dynamic critical exponents of these thermal avalanches, both during the primary creep transient and the ultimate steady-state. I will discuss connections to the glass transition, where it was recently suggested that dynamical heterogeneity may be driven by slow thermal avalanches [4].

[1] D. Korchinski and J. Rottler. Phys. Rev. E 106, 034103 (2022).

[2] M. Popović, T. W. J. de Geus, W. Ji, and M. Wyart. Phys. Rev. E 104, 025010 (2021).

[3] D. Shohat, Y. Friedman, and Y. Lahini. Nat. Phys. 1 (2023).

[4] A. Tahaei et al., Phys. Rev. X 13, 031034 (2023).