Breakdown of bosonic Thouless pump due to interaction in a quasiperiodic lattice

TL;DR

This paper studies how weak interactions disrupt the quantized charge transport in a bosonic quasiperiodic lattice, revealing interaction-dependent breakdown and revival of quantization, with implications for many-body Floquet systems.

Contribution

It demonstrates the breakdown and revival of Thouless pump quantization in interacting bosonic systems, highlighting the role of doublon channels and band-dependent doublon stability.

Findings

Quantization breaks down at weak interactions.

Quantization revives at large hardcore interactions.

Doublons in different bands show asymmetric stability.

Abstract

We investigate the effect of inter-particle interaction on the quantized Thouless pump in the bosonic quasiperiodic Aubry-Andr{\'e} model and find that the quantization of the pumped charge breaks down already for weak interactions. Furthermore, the pumped charge undergoes sharp changes as a function of interaction strength that we can attribute to the closing of specific doublon channels. As expected, the quantization revives in the hard-core limit at very large interaction strengths where the bosons are subject to a hardcore constraint. Interestingly, the stability of isolated doublons under the pump depends on the band they are in. For repulsive interactions and a suitably fixed pump period, doublons in the lowest band are pumped stably while doublons in higher bands dissociate during the pump with one particle decaying into a lower band. This asymmetry leads to the decay of the total energy over time, in stark contrast to the typical Floquet heating expected for a driven many-body system.