Interaction instability of localization in quasiperiodic systems

TL;DR

This paper demonstrates that in quasiperiodic systems, small interactions can cause a sudden transition from localized to diffusive behavior, revealing an inherent instability in many-body localization.

Contribution

It provides the first explicit example of a quasiperiodic system where interactions cause a discontinuous change in transport properties, challenging assumptions about stability of many-body localization.

Findings

Interaction causes abrupt transition from localization to diffusion.

Transport properties can be engineered by modifying a few lattice sites.

No general stability theorem exists for many-body localization in quasiperiodic systems.

Abstract

Integrable models form pillars of theoretical physics because they allow for full analytical understanding. Despite being rare, many realistic systems can be described by models that are close to integrable. Therefore, an important question is how small perturbations influence the behavior of solvable models. This is particularly true for many-body interacting quantum systems where no general theorems about their stability are known. Here, we show that no such theorem can exist by providing an explicit example of a one-dimensional many-body system in a quasiperiodic potential whose transport properties discontinuously change from localization to diffusion upon switching on interaction. This demonstrates an inherent instability of a possible many-body localization in a quasiperiodic potential at small interactions. We also show how the transport properties can be strongly modified by engineering potential at only a few lattice sites.