Geometrical pumping with a Bose-Einstein condensate

TL;DR

This paper demonstrates a quantum geometric charge pump using a Bose-Einstein condensate in a bipartite magnetic lattice, highlighting non-quantized, geometry-driven atomic displacement within a single momentum state.

Contribution

It introduces a novel geometric charge pump for a BEC in a single momentum state, emphasizing local band structure properties over topological quantization.

Findings

Observed non-quantized atomic displacement per cycle

Demonstrated temporal modulation of atomic polarization

Established a link between geometry and charge transport in BECs

Abstract

We realized a quantum geometric "charge" pump for a Bose-Einstein condensate (BEC) in the lowest Bloch band of a novel bipartite magnetic lattice. Topological charge pumps in filled bands yield quantized pumping set by the global -- topological -- properties of the bands. In contrast, our geometric charge pump for a BEC occupying just a single crystal momentum state exhibits non-quantized charge pumping set by local -- geometrical -- properties of the band structure. Like topological charge pumps, for each pump cycle we observed an overall displacement (here, not quantized) and a temporal modulation of the atomic wavepacket's position in each unit cell, i.e., the polarization.