Modified Matthiessen's rule: More scattering leads to less resistance

We study the breaking of integrability by a finite density of dilute impurities, specifically the emerging diffusive transport. Provided the distance between impurities (localized perturbations) is large, one would expect the scattering rates to be additive, and therefore, the resistivity to be proportional to the number of impurities (the so-called Matthiessen's rule). We show that this is, in general, not the case. If transport is anomalous in the original integrable system without impurities, the diffusion constant in the nonintegrable system at low impurity density has a nontrivial power-law dependence on the impurity density, with the power being determined by the dynamical scaling exponent of anomalous transport. We also find a regime at high impurity density in which, counterintuitively, adding more impurities to an already diffusive system increases transport rather than decreases it.

Automated summary

We study the breaking of integrability by a finite density of dilute impurities, specifically the emerging diffusive transport. If transport is anomalous in the original integrable system without impurities, the diffusion constant in the nonintegrable system at low impurity density has a nontrivial power-law dependence on the impurity density. At high impurity density, adding more impurities to an already diffusive system increases transport rather than decreases it.