Interplay of Dirac electrons and magnetism in AMnBi2 (A=Ca, Sr)

TL;DR

This study investigates how Dirac electrons interact with magnetic properties in AMnBi2 compounds, revealing enhanced exchange coupling and charge-gap opening, which advances understanding of magnetic Dirac materials and their potential applications.

Contribution

First detailed analysis of exchange energies in magnetic Dirac materials, showing how Dirac layers influence magnetic interactions and charge-gap formation.

Findings

Dirac layers significantly enhance magnetic exchange coupling.

Charge-gap opens along the Dirac locus due to magnetic interactions.

Magnetic Dirac materials offer a platform for spin-Fermion physics and device applications.

Abstract

Dirac materials exhibit intriguing low-energy carrier dynamics that offer a fertile ground for novel physics discovery. Of particular interest is the interplay of Dirac carriers with other quantum phenomena, such as magnetism. Here we report on a two-magnon Raman scattering study of AMnBi2 (A=Ca, Sr), a prototypical magnetic Dirac system comprising alternating Dirac-carrier and magnetic layers. We present the first accurate determination of the exchange energies in these compounds and, by comparison to the reference compound BaMn2Bi2, we show that the Dirac-carrier layers in AMnBi2 significantly enhance the exchange coupling between the magnetic layers, which in turn drives a charge-gap opening along the Dirac locus. Our findings break new grounds in unveiling the fundamental physics of magnetic Dirac materials, which offer a novel platform for probing a distinct type of spin-Fermion interaction. The outstanding properties of these materials allow a delicate manipulation of the interaction between the Dirac carriers and magnetic moments, thus holding great promise for applications in magnetic Dirac devices.