Magnon spin Hall magnetoresistance of a gapped quantum paramagnet

TL;DR

This paper investigates how spin transport in a gapped quantum paramagnet, modeled as a magnonic Mott insulator, leads to a spin Hall magnetoresistance that depends on magnetic field strength, with implications for spintronics.

Contribution

It introduces a model for spin transport in a gapped quantum paramagnet as a magnonic Mott insulator and predicts a field-dependent spin Hall magnetoresistance.

Findings

Spin current depends on magnetic field magnitude.

Strongly interacting magnons induce field-dependent magnetoresistance.

Potential for electrical detection of quantum magnetic phases.

Abstract

Motivated by recent experimental work, we consider spin transport between a normal metal and a gapped quantum paramagnet. We model the latter as the magnonic Mott-insulating phase of an easy-plane ferromagnetic insulator. We evaluate the spin current mediated by the interface exchange coupling between the ferromagnet and the adjacent normal metal. For the strongly interacting magnons that we consider, this spin current gives rise to a spin Hall magnetoresistance that strongly depends on the magnitude of the magnetic field, rather than its direction. This Letter may motivate electrical detection of the phases of quantum magnets and the incorporation of such materials into spintronic devices.