A topological classification of interaction-driven spin pumps

TL;DR

This paper classifies interaction-driven spin pumps in one-dimensional insulators with time-reversal symmetry, revealing multiple classes with quantized spin pumping properties influenced by many-body interactions.

Contribution

It introduces a topological classification of spin pumps considering interactions, expanding understanding beyond non-interacting systems.

Findings

Multiple classes of spin pumps with different quantized spin transfer behaviors.

Presence of a trivial class that does not pump quantized spin.

Example of a spin pump transferring spin /2 without charge transfer.

Abstract

When adiabatically varied in time, certain one-dimensional band insulators allow for the quantized noiseless pumping of spin even in the presence of strong spin orbit scattering. These spin pumps are closely related to the quantum spin Hall system, and their properties are protected by a time-reversal restriction on the pumping cycle. In this paper we study pumps formed of one-dimensional insulators with a time-reversal restriction on the pumping cycle and a bulk energy gap which arises due to interactions. We find that the correlated gapped phase can lead to novel pumping properties. In particular, systems with $d$ different ground states can give rise to $d+1$ different classes of spin pumps, including a trivial class which does not pump quantized spin and $d$ non-trivial classes allowing for the pumping of quantized spin $\hbar/n $ on average per cycle, where $1\leq n\leq d$. We discuss an example of a spin pump that transfers on average spin $ \hbar/2$ without transferring charge.