Dynamics of weakly interacting bosons in optical lattices with flux

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 quasimomentum space. Our results also show that weak interactions can suppress the contribution of some higher-order nontopological terms in favor of the topological part of the effective model.

Bosonic fractional quantum Hall states in driven optical lattices

“…A highly relevant question that we have not tackled and that we postpone to future investigation, concerns suitable experimental probes of topological features. The recent progress in the field has led to the development of several detection protocols specially suited for the coldatom systems [59][60][61][62][63][64]. For the type of systems considered in this paper, the most promising are results of the recent study [64] showing that fractional excitations can be probed even in small systems of several bosons.…”

Transport properties of cold atoms in optical lattice

“…The cold atoms can pass through the lattice under the effect of tunneling between neighboring lattice sites with a rate J and experience an on-site interaction U [15,20]. By coupling a pumped atom laser to the boundary sites of the lattice system, the cold atoms can move in and out via boundary sites of the lattice [17,21,22]. With the technique of engineering reservoir, distance-selective dissipation of atoms can be realized in the system [15].…”

Dissipative dynamics of cold atoms in an optical lattice

“…The atoms can move through the lattice by tunneling between neighboring lattice sites with a rate J and experience an on-site interaction U [30]. The atoms can also move in and out via boundary sites of the lattice modeled by external drivings [16,31]. With the technique of engineering reservoir, a distance-selective loss of atoms can be realized for such a system [32].…”