Long-range p-d exchange interaction in a ferromagnet-semiconductor hybrid structure

TL;DR

This study reveals a long-range, robust p-d exchange interaction in a ferromagnet-semiconductor hybrid structure, mediated by elliptically polarized phonons, challenging the typical short-range nature of such interactions.

Contribution

It demonstrates a long-range p-d exchange interaction in a hybrid structure, mediated by phonons, which is a novel finding compared to the expected short-range exchange.

Findings

Long-range coupling persists over more than 10 nm barrier.

Spin polarization of holes is induced by phonon-mediated exchange.

Contradicts the typical exponential decay of exchange with distance.

Abstract

Hybrid structures synthesized from different materials have attracted considerable attention because they may allow not only combination of the functionalities of the individual constituents but also mutual control of their properties. To obtain such a control an interaction between the components needs to be established. For coupling the magnetic properties, an exchange interaction has to be implemented which typically depends on wave function overlap and is therefore short-ranged, so that it may be compromised across the interface. Here we study a hybrid structure consisting of a ferromagnetic Co-layer and a semiconducting CdTe quantum well, separated by a thin (Cd,Mg)Te barrier. In contrast to the expected p-d exchange that decreases exponentially with the wave function overlap of quantum well holes and magnetic Co atoms, we find a long-ranged, robust coupling that does not vary with barrier width up to more than 10 nm. We suggest that the resulting spin polarization of the holes is induced by an effective p-d exchange that is mediated by elliptically polarized phonons.