Interactions Enable Thouless Pumping in a Nonsliding Lattice

Abstract

A topological “Thouless” pump represents the quantized motion of particles in response to a slow,cyclic modulation of external control parameters. The Thouless pump, like the quantum Hall effect, is offundamental interest in physics, because it links physically measurable quantities, such as particle currents,to geometric properties of the experimental system, which can be robust against perturbations and, thus,technologically useful. So far, experiments probing the interplay between topology and interparticleinteractions have remained relatively scarce. Here, we observe a Thouless-type charge pump in which theparticle current and its directionality inherently rely on the presence of strong interactions. Experimentally,we utilize a two-component Fermi gas in a dynamical superlattice which does not exhibit a sliding motionand remains trivial in the single-particle regime. However, when tuning interparticle interactions from zeroto positive values, the system undergoes a transition from being stationary to drifting in one direction,consistent with quantized pumping in the first cycle. Remarkably, the topology of the interacting pumptrajectory cannot be adiabatically connected to a noninteracting limit, highlighted by the fact that only oneatom is transferred per cycle. Our experiments suggest that Thouless charge pumps are promising platformsto gain insights into interaction-driven topological transitions and topological quantum matter.