Unconventional interlayer exchange coupling via chiral phonons in synthetic magnetic oxide heterostructures

TL;DR

This paper demonstrates a novel chiral phonon-mediated interlayer exchange interaction in magnetic heterostructures, revealing how chiral phonons influence magnetic order and spin dynamics at the atomic scale.

Contribution

It provides the first experimental evidence of chiral phonon-spin coupling and its role in mediating interlayer exchange in synthetic magnetic heterostructures.

Findings

Observation of magnetic moment rotation with spacer thickness

Detection of phonon Zeeman effects confirming chiral phonon-spin coupling

Identification of spin spiral states induced by chiral phonons

Abstract

Chiral symmetry breaking of phonons plays an essential role in emergent quantum phenomena owing to its strong coupling to spin degree of freedom. However, direct experimental evidence of the chiral phonon-spin coupling is lacking. In this study, we report a chiral phonon-mediated interlayer exchange interaction in atomically controlled ferromagnetic metal (SrRuO3)-nonmagnetic insulator (SrTiO3) heterostructures. Owing to the unconventional interlayer exchange interaction, we have observed rotation of magnetic moments as a function of nonmagnetic insulating spacer thickness, resulting in a spin spiral state. The chiral phonon-spin coupling is further confirmed by phonon Zeeman effects. The existence of the chiral phonons and their interplay with spins along with our atomic-scale heterostructure approach open a window to unveil the crucial roles of chiral phonons in magnetic materials.