Unified view of avalanche criticality in sheared glasses

Area of Science:

• Condensed Matter Physics
• Materials Science
• Statistical Mechanics

Background:

• Plastic events in sheared glasses are modeled as avalanches with power-law size distributions.
• Existing theories like mean-field depinning (MFD) predict a universal critical exponent (τ=1.5), but experimental and numerical results vary, leading to debate on criticality and universality.

Purpose of the Study:

• To achieve a unified understanding of avalanche criticality in sheared glasses.
• To conduct a high-precision numerical investigation of avalanches in Lennard-Jones glasses under shear.
• To resolve discrepancies in reported critical exponent values and understand the underlying physics.

Main Methods:

• Athermal quasistatic shear simulations of Lennard-Jones glasses.
• High-precision measurement of avalanche sizes and distributions.
• Analysis of avalanche statistics in both steady and elastic regimes, including the first avalanche event.
• Investigation of the fractal dimension of avalanches.

Main Results:

• The steady-state avalanche critical exponent (τ) precisely matches the MFD prediction (τ=1.5).
• Two distinct types of avalanches were identified, explaining the nonuniversal behavior of size distributions and prior conflicting results.
• The system transitions from an off-critical unperturbed state to a critical state as shear is applied.
• The degree of criticality, quantified by fractal dimension, develops with shear and saturates in the steady state.

Conclusions:

• The study provides a unified understanding of avalanche criticality in sheared glasses, reconciling previous discrepancies.
• The identified binariness of avalanches is crucial for understanding their statistical behavior and the emergence of criticality under shear.
• The findings confirm the universality of the critical exponent in the critical state, consistent with MFD theory.