Excitation spectra in crystal plasticity

TL;DR

This paper investigates the excitation spectra in crystal plasticity, revealing a singularity in excitation stress distributions that links crystal deformation behavior to amorphous materials and spin glasses, advancing understanding of criticality in plastic deformation.

Contribution

It provides the first detailed analysis of excitation spectra in dislocation ensembles in 2D and 3D, connecting critical phenomena in crystals to those in amorphous systems.

Findings

Presence of a singularity in excitation stress distribution

Similarity of excitation spectra to amorphous plasticity and spin glasses

Explanation of extended criticality in bursty crystal plasticity

Abstract

Plastically deforming crystals exhibit scale-free fluctuations that are similar to those observed in driven disordered elastic systems close to depinning, but the nature of the yielding critical point is still debated. Here, we study the marginal stability of ensembles of dislocations and compute their excitation spectrum in two and three dimensions. Our results show the presence of a singularity in the distribution of {\it excitation stresses}, i.e., the stress needed to make a localized region unstable, that is remarkably similar to the one measured in amorphous plasticity and spin glasses. These results allow us to understand recent observations of extended criticality in bursty crystal plasticity and explain how they originate from the presence of a pseudogap in the excitation spectrum.