1 Biocomplexity, The Niels Bohr Institute, Faculty of Science, Københavns Universitet2 The Niels Bohr Institute, Faculty of Science, Københavns Universitet3 Physics of Geological Processes, Department of Physics, University of Oslo, Oslo, Norway4 Department of Physics, University of Illinois at Urbana-Champaign, Loomis Laboratory of Physics5 Biocomplexity, The Niels Bohr Institute, Faculty of Science, Københavns Universitet
Plastic deformation mediated by collective dislocation dynamics is investigated in the two-dimensional phase-field crystal model of sheared single crystals. We find that intermittent fluctuations in the dislocation population number accompany bursts in the plastic strain-rate fluctuations. Dislocation number fluctuations exhibit a power-law spectral density 1/f2 at high frequencies f. The probability distribution of number fluctuations becomes bimodal at low driving rates corresponding to a scenario where low density of defects alternates at irregular times with high populations of defects. We propose a simple stochastic model of dislocation reaction kinetics that is able to capture these statistical properties of the dislocation density fluctuations as a function of shear rate.