Spectral hole burning to probe the nature of unjamming (Payne effect) in particle-filled elastomers

The Payne effect is a low-strain hysteretic softening in particle-filled elastomers which we recognize as part of jamming physics. We find that aging at a fixed oscillatory strain produces a hole in the unjamming loss modulus spectrum which is localized near the aging strain for a silica-filled elastomer. This cannot be predicted by any existing Payne effect model. By applying the Einstein fluctuation-dissipation relation and comparing our findings to nonequilibrium glassy behavior, we show that oscillatory strain amplitude in particle-filled elastomers can be interpreted as an effective temperature.