Nontrivial scaling exponents of dislocation avalanches in microplasticity

Crystal plasticity causes structural fluctuations that can be scale-free and therefore admit power-law distributions. Numerous experiments, modeling, and theory have reported a scaling exponent that is in good agreement with mean-field predictions or a jamming-unjamming scenario. Via experiments on pure single crystals, we show here that the scaling exponent of a stress-integrated distribution for dislocation-avalanche sizes is nontrivial and can be in agreement with both models by admitting values between 1.0 and 2.3. This range is dictated by the structure and orientation of the deforming crystal, as long as the applied rate is below a critical value. For the highest symmetry tested, plastic strain can drive a change from truncated power-law scaling to pure exponential scaling. These findings show how the same crystal may yield different scaling exponents depending on intrinsic and extrinsic factors.