Occupation-selective topological pumping from Floquet gauge fields

TL;DR

This paper introduces a novel form of topological pumping driven by occupation-dependent gauge fields, enabling occupation-selective quantized transport in a Floquet-engineered ultracold atom system, distinct from traditional band topology.

Contribution

It demonstrates that dynamical, occupation-conditioned tunneling can induce topological phases and quantized transport for bound states, revealing a new mechanism beyond single-particle band topology.

Findings

Two-body bound states have distinct Chern numbers from single particles.

Quantized transport occurs even when single-particle pump is trivial.

Occupation-selective responses persist across higher-occupancy bound states.

Abstract

Topological pumping is conventionally governed by single-particle band topology. Here we show that promoting tunneling to a dynamical, occupation-conditioned variable fundamentally reshapes this paradigm, leading to occupation-selective topological pumping. In a periodically driven one-dimensional superlattice with density-dependent hopping, two-body bound states (doublons) acquire Chern numbers distinct from those of single particles and exhibit quantized transport even when the single-particle pump is trivial, including counter-propagating responses. We identify a dynamical-gauge-field mechanism that induces topological phase transitions in the bound-state sector absent from the single-particle spectrum. Furthermore, the gauge field concentrates Berry curvature into sharply localized resonant regions without compromising adiabatic quantization. A Floquet realization with ultracold atoms is proposed to realize such occupation-selective pumping. Our results reveal a mechanism for occupation-selective topological responses that can persist across higher-occupancy bound states.