Interactions enable Thouless pumping in a nonsliding lattice

TL;DR

This paper demonstrates a topological charge pump in a strongly interacting Fermi gas, revealing interaction-driven topological transitions and showcasing robustness of quantized particle transport in a non-sliding lattice.

Contribution

It reports the first experimental observation of a Thouless pump relying on strong interactions in a non-sliding lattice, highlighting a new interaction-driven topological transition.

Findings

Particle current depends on strong interactions.

Transition from stationary to drifting state with interaction tuning.

Only one atom transferred per cycle, indicating non-trivial topology.

Abstract

A topological 'Thouless' pump represents the quantised motion of particles in response to a slow, cyclic modulation of external control parameters. The Thouless pump, like the quantum Hall effect, is of fundamental 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 inter-particle interactions have remained relatively scarce. Here we observe a Thouless-type charge pump in which the particle current and its directionality inherently rely on the presence of strong interactions. Experimentally, we utilise a two-component Fermi gas in a dynamical superlattice which does not exhibit a sliding motion and remains trivial in the single-particle regime. However, when tuning interparticle interactions from zero to positive values, the system undergoes a transition from being stationary to drifting in one direction, consistent with quantised pumping in the first cycle. Remarkably, the topology of the interacting pump trajectory cannot be adiabatically connected to a non-interacting limit, highlighted by the fact that only one atom is transferred per cycle. Our experiments suggest that Thouless charge pumps are promising platforms to gain insights into interaction-driven topological transitions and topological quantum matter.