Restoring Ergodicity in a Strongly Disordered Interacting Chain

We consider a chain of interacting fermions with random disorder that was intensively studied in the context of many-body localization. We show that only a small fraction of the two-body interaction represents a true local perturbation to the Anderson insulator. While this true perturbation is nonzero at any finite disorder strength W, it decreases with increasing W. This establishes a view that the strongly disordered system should be viewed as a weakly perturbed integrable model, i.e., a weakly perturbed Anderson insulator. As a consequence, the latter can hardly be distinguished from a strictly integrable system in finite-size calculations at large W. We then introduce a rescaled model in which the true perturbation is of the same order of magnitude as the other terms of the Hamiltonian, and show that the system remains ergodic at arbitrary large disorder.

Automated summary

In this study, we investigate a chain of interacting fermions with random disorder in the context of many-body localization. Our findings indicate that only a small fraction of the interaction can be considered as a true local perturbation to the Anderson insulator, and this perturbation decreases with increasing disorder strength. This suggests that strongly disordered systems can be viewed as weakly perturbed integrable models, namely weakly perturbed Anderson insulators. Additionally, we introduce a rescaled model where the true perturbation is of the same order of magnitude as the other terms in the Hamiltonian, and we demonstrate that the system remains ergodic at arbitrary large disorder.