Trimer Thouless Pump: Topology, Symmetries, and Multigap Structure
Topological charge pumping is paradigmatically understood through two-band systems such as the Rice-Mele model, which are intrinsically restricted to a single independent pumping channel. In this work, we introduce the Trimer Thouless Pump (TTP), a minimal three-band generalization that exhibits genuinely multigap topological transport. By subjecting a one-dimensional three-site lattice to cyclic adiabatic modulations of its hopping amplitudes and antisymmetric onsite potentials, we explore a topological regime characterized by two independent bulk gaps. We show that the quantized charge transport is driven by highly localized Berry curvature hotspots corresponding to effective two-level Dirac avoided crossings on the parameter torus. Crucially, we demonstrate that the middle energy band acts as a geometric mediator: it facilitates the exchange of quantized Berry flux between the upper and lower bands while maintaining a net zero Chern number itself. This bulk topology is corroborated by the spectral flow of boundary-localized edge states traversing multiple gaps. Furthermore, we map the topological phase diagram as a function of central-site detuning, illustrating a band-selective transfer of topological invariants across discrete phase transitions. Finally, we propose a concrete experimental protocol to realize the TTP and observe its multigap charge transport using ultracold atoms in phase-controlled optical superlattices.