Transport through interacting defects and lack of thermalisation

TL;DR

This paper investigates how localized defects in 1D integrable systems cause thermalization at the defect site but preserve non-thermal outgoing flows, revealing a generalized boundary thermal resistance effect.

Contribution

It demonstrates the interplay between chaos and integrability in 1D systems with defects, combining numerical simulations and Boltzmann equation analysis to understand thermalization and non-thermal transport.

Findings

Large defects induce local thermalization.

Outgoing flow remains non-thermal due to boundary resistance.

Results combine simulations with Boltzmann equation analysis.

Abstract

We consider 1D integrable systems supporting ballistic propagation of excitations, perturbed by a localised defect that breaks most conservation laws and induces chaotic dynamics. Focusing on classical systems, we study an out-of-equilibrium protocol engineered activating the defect in an initially homogeneous and far from the equilibrium state. We find that large enough defects induce full thermalisation at their center, but nonetheless the outgoing flow of carriers emerging from the defect is non-thermal due to a generalization of the celebrated Boundary Thermal Resistance effect, occurring at the edges of the chaotic region. Our results are obtained combining ab-initio numerical simulations for relatively small-sized defects, with the solution of the Boltzmann equation, which becomes exact in the scaling limit of large, but weak defects.