Demonstration of returning Thouless pump in a Berry dipole system

TL;DR

This paper experimentally demonstrates a novel returning Thouless pump mediated by a Berry dipole in a 1D acoustic waveguide, showcasing unique edge mode dynamics and pseudospin flipping, expanding the understanding of topological transport mechanisms.

Contribution

It introduces the first experimental realization of a Berry dipole-mediated returning Thouless pump, revealing new topological transport phenomena beyond monopole-based systems.

Findings

Demonstrated RTP in a 1D acoustic waveguide array

Observed edge mode delocalization and return during adiabatic cycle

Identified pseudospin flipping as a characteristic feature

Abstract

The Thouless pump, a cornerstone of topological physics, enables unidirectional quantized wave/particle transport via geometric Berry phase engineering in periodically driven systems. While decades of research have been dedicated to monopole-mediated pumping, mechanisms governed by higher-order singularities like Berry dipoles remain unexplored. Here, we report the experimental demonstration of a Berry-dipole-mediated returning Thouless pump (RTP) in a 1D acoustic waveguide array achieved through adiabatic encircling of a Berry dipole singularity. During this adiabatic cycle, an initial edge-localized mode first delocalizes into the bulk and eventually returns to the original edge, marking the characteristic signature of the RTP. Notably, this RTP exhibits an interesting feature of pseudospin flipping. The demonstrated RTP contrasts sharply with the well-studied monopole-governed pumps that feature unidirectional transport.