Dynamics of weakly interacting bosons in optical lattices with flux

TL;DR

This paper studies how weak interactions among bosons in driven optical lattices affect the measurement of topological properties like the Chern number, revealing that moderate repulsion can aid in clearer topological signal detection.

Contribution

It provides a detailed analysis of the impact of weak interactions on bosonic dynamics in optical lattices, highlighting their role in enhancing topological measurements.

Findings

Interactions cause redistribution of atoms over topological bands.

Moderate repulsion flattens the quasi-momentum distribution.

Weak interactions suppress non-topological contributions, emphasizing topological effects.

Abstract

Realization of strong synthetic magnetic fields in driven optical lattices has enabled implementation of topological bands in cold-atom setups. A milestone has been reached by a recent measurement of a finite Chern number based on the dynamics of incoherent bosonic atoms. The measurements of the quantum Hall effect in semiconductors are related to the Chern-number measurement in a cold-atom setup, however, the design and complexity of the two types of measurements are quite different. Motivated by these recent developments, we investigate the dynamics of weakly interacting incoherent bosons in a two-dimensional driven optical lattice exposed to an external force, which provides a direct probe of the Chern number. We consider a realistic driving protocol in the regime of high driving frequency and focus on the role of weak repulsive interactions. We find that interactions lead to the redistribution of atoms over topological bands both through the conversion of interaction energy into kinetic energy during the expansion of the atomic cloud and due to an additional heating. Remarkably, we observe that the moderate atomic repulsion facilitates the measurement by flattening the distribution of atoms in the quasi-momentum space. Our results also show that weak interactions can suppress the contribution of some higher-order non-topological terms in favor of the topological part of the effective model.