Topological charge pumping in the interacting bosonic Rice-Mele model

TL;DR

This paper studies topological charge pumping in an interacting bosonic Rice-Mele model, demonstrating quantized transport that persists under certain conditions and linking it to entanglement spectrum properties.

Contribution

It introduces a many-body topological invariant for charge pumping in interacting bosons and analyzes its behavior across different interaction regimes.

Findings

Charge pumping remains quantized when avoiding the superfluid phase.

Quantized charge can be explained by single-particle Berry curvature in the hardcore limit.

Entanglement spectrum exhibits a winding that encodes the quantized charge transport.

Abstract

We investigate topological charge pumping in a system of interacting bosons in the tight-binding limit, described by the Rice-Mele model. An appropriate topological invariant for the many-body case is the change of polarization per pump cycle, which we compute for various interaction strengths from infinite-size matrix-product-state simulations. We verify that the charge pumping remains quantized as long as the pump cycle avoids the superfluid phase. In the limit of hardcore bosons, the quantized pumped charge can be understood from single-particle properties such as the integrated Berry curvature constructed from Bloch states, while this picture breaks down at finite interaction strengths. These two properties -- robust quantized charge transport in an interacting system of bosons and the breakdown of a single-particle invariant -- could both be measured with ultracold quantum gases extending a previous experiment [Lohse et al., Nature Phys. 12, 350 (2016)]. Furthermore, we investigate the entanglement spectrum of the Rice-Mele model and argue that the quantized charge pumping is encoded in a winding of the spectral flow in the entanglement spectrum over a pump cycle.