# Diffusive transport in a quasiperiodic Fibonacci chain: absence of many-body localization at small interactions

## TL;DR

This study investigates magnetization transport in a quasiperiodic Fibonacci spin chain, revealing that weak interactions induce diffusive behavior and contrasting with subdiffusive transport in random potentials.

## Contribution

It demonstrates that weak interactions cause diffusive transport in a quasiperiodic Fibonacci chain, unlike the subdiffusive behavior seen in random potentials, and highlights limitations of mean-field approaches.

## Key findings

- Weak interactions induce diffusion in Fibonacci chains.
- Transport remains subdiffusive in random potentials at small interactions.
- Mean-field theory fails to capture diffusion in quasiperiodic systems.

## Abstract

We study high-temperature magnetization transport in a many-body spin-1/2 chain with on-site quasiperiodic potential governed by the Fibonacci rule. In the absence of interactions it is known that the system is critical with the transport described by a continuously varying dynamical exponent (from ballistic to localized) as a function of the on-site potential strength. Upon introducing weak interactions, we find that an anomalous noninteracting dynamical exponent becomes diffusive for any potential strength. This is borne out by a boundary-driven Lindblad dynamics as well as unitary dynamics, with agreeing diffusion constants. This must be contrasted to random potential where transport is subdiffusive at such small interactions. Mean-field treatment of the dynamics for small U always slows down the non-interacting dynamics to subdiffusion, and is therefore unable to describe diffusion in an interacting quasiperiodic system. Finally, briefly exploring larger interactions we find a regime of interaction-induced subdiffusive dynamics, despite the on-site potential itself having no "rare-regions".